Nuvo vs HRV Works: Daily Biological Age or Calendar Stress + Bio Age?

Pick HRV Works for Apple Watch calendar stress and a wearable bio age. Pick Nuvo for a daily 21-biomarker score with optional labs, $24.99/yr.

Written by the Nuvo Longevity editorial team at Firefly Labs LLC.

Pick HRV Works if you want an Apple Watch app that connects your calendar to stress: meeting-stress prediction, a recovery score against a 60-day HRV baseline, habit impact, body battery, and a wearable biological age with an aging-pace / 10-year projection. Pick Nuvo if you want a daily biological age on iPhone and Apple Watch from 21 biomarkers — HealthKit plus optional lab PDF — with on-device AI, no account, Apple’s privacy label Data Not Collected, and $24.99/year after a 7-day trial. They overlap the Apple Watch longevity buyer. They are partial substitutes on the headline “biological age,” and complementary if you want calendar-stress coaching beside a 21-biomarker score that can include labs. HRV Works’ biological age is a wearable composite (VO2 max, resting heart rate, sleep quality, and activity on the public weights). It is not Nuvo’s 21-biomarker daily score.

Written by the Nuvo Longevity editorial team at Firefly Labs LLC, the developer of Nuvo. HRV Works details below are taken from the public homepage (hrv.works/en), the privacy policy and terms of service (effective 1 December 2025), the HRV Works essay on wearable biological age, and the TestFlight link printed on that homepage, checked 15 October 2026. This page is educational and is not medical advice. A wearable composite age is not a clinical assay, and Nuvo’s daily score is not a substitute for a clinician.

What each product actually sells

HRV Works: calendar stress, recovery, and a wearable biological age

HRV Works markets itself as an Apple Watch app. The homepage headline is “See burnout coming. Stop it cold,” and the job underneath is schedule plus stress: “We connect your schedule to your stress data.” A footnote on that page says hrv.works “securely integrates with Apple HealthKit” and that “All data is processed on-device.” A separate badge says “100% On-Device” and “Your data never leaves your device.” The privacy policy describes a different stack; that contradiction is in the privacy section below. We cite both documents.

What the homepage actually sells, checked 15 October 2026:

• Biological Age — “Know your body’s true age—not your calendar age. Based on VO2 Max, resting heart rate, and sleep quality.” The same page’s “How We Calculate Bio Age” section publishes weights: 40% VO2 Max, 25% resting heart rate, 20% sleep quality, 15% activity level. The short card names three inputs; the weights add activity. That is a wearable composite.
• Recovery score — compare HRV with a 60-day baseline for training readiness.
• Calendar and meeting stress — “Connected Calendar,” predicted stress for a meeting, and a Context Engine that maps calendar events to HRV (“which tasks drain your energy and whose meetings stress you out”).
• Morning brief, live stress monitor, pattern detection, and breathing / walk recommendations when the page’s copy says you are stressed, recovered, or depleted.
• Habit impact — alcohol, coffee, and late meals. The page illustrates this with a “+2.3 days aged” example for “last night’s impact.” Treat that figure as marketing UI, not a published study result.
• Aging pace / 10-year projection — “Pace of 0.9 = only 9 years aged in a decade” is the example on the page.
• Body battery — available energy from 0–100% “based on sleep recovery data.”
• Background HRV while you sleep, on the Apple Watch you already wear. The page says no extra hardware.

The public comparison table on that homepage lists Monthly Price $4.99 for HRV Works, next to Whoop at $30 and Oura at $5.99. Those Whoop and Oura numbers are HRV Works’ table. This page does not re-verify them. The same table checks calendar integration, meeting-stress prediction, fatigue root-cause analysis, 100% on-device processing, and no dedicated hardware. The homepage also prints “500+ Testers” and “Beta Feedback,” and the download control is a TestFlight link, not an App Store URL.

We did not find a public App Store listing named HRV Works on 15 October 2026. iTunes Search for “HRV Works” in the United States, Korea, the United Kingdom, Japan, and Germany did not return an app by that title, and the homepage does not link to apps.apple.com. Without that listing we also did not find an Apple privacy nutrition label, a yearly subscription price, or an App Store rating count. The TestFlight page for the homepage’s invite, checked the same day, said: “This beta isn’t accepting any new testers right now.” The marketing page still said the beta was open and cited 500+ testers. Both pages were public on the check date.

Their essay Biological Age: The “Speed of Aging” Found in 210,000 Wrists discusses PpgAge (Miller et al., Nature Communications, 2025; DOI 10.1038/s41467-025-64275-4), a wrist-PPG aging clock from the Apple Heart and Movement Study. The essay itself says PpgAge “isn’t explicitly shown in the Apple Watch app” as a biological-age number yet. Do not treat the homepage’s 40/25/20/15 wearable composite as that paper’s model. The homepage lists the Norwegian HUNT Study, the FRIEND Registry, and JACC 2018 as a “research foundation.” It does not, on that page, show how those papers become the four weights.

The privacy policy (effective 1 December 2025) calls HRV Works an iOS application. The terms (same date) say the app provides HRV analysis for wearable users and name Apple HealthKit as a third-party service. Contact on both pages is taeho@taeho.io. We did not find a separate legal entity name beyond “HRV Works.”

HRV Works, on the pages above, does not sell a 21-biomarker daily score and does not describe optional lab PDF upload. If the job is “which meetings stressed me, and what does a Watch-only age composite say,” that is the product they describe.

Nuvo: a daily 21-biomarker score

Nuvo Longevity (App Store: Nuvo: Longevity Coach, id 6762535065) is an iPhone and Apple Watch app. It calculates a daily biological age from 21 biomarkers: Apple Health / HealthKit data from Apple Watch, Oura, or Garmin, plus optional lab PDF upload so conventional results you already paid for (HbA1c, fasting glucose, HDL, CRP, creatinine, and more) sit in the same score.

Coaching runs as on-device private AI (Nuvo Intelligence). There is no account. Apple’s privacy nutrition label for Nuvo is Data Not Collected. Health data stays on the phone, is not sent to Nuvo servers, and is not sold. Price is $4.99/month or $24.99/year after a 7-day trial — $24.99/year is $2.08/month billed annually. Nuvo is not Android. Nuvo does not predict which calendar meeting will spike your stress, and it does not replace a 60-day HRV recovery coach.

Nuvo is not HRV Works’ wearable composite or its calendar layer. If the job is “one daily biological age from 21 biomarkers, including optional labs, privately, on the phone you already carry,” that is Nuvo. Download app. For the wider field, see our 2026 biological age app comparison. For another Apple Watch training coach, see Nuvo vs Athlytic. For another Watch biological-age app, see SuperAge vs Nuvo. For a strap rather than a Watch app, see Nuvo vs WHOOP.

Comparison table

What each biological age actually measures

HRV Works’ homepage age is a weighted wearable composite: cardiorespiratory fitness (VO2 max, 40%), resting heart rate (25%), sleep quality (20%), and activity (15%). VO2 max is a real longevity input — how it relates to biological age is covered in VO2 max and biological age — and it is still one wearable signal. Resting heart rate, sleep, and activity are the same class of input. Together they can move every day the Watch records them. They do not include HbA1c, CRP, lipids, or kidney markers unless some page we did not find says so. We did not find that page.

Their PpgAge essay is about a research clock from wrist photoplethysmography in the Apple Heart and Movement Study (n = 213,593 in the paper). The essay says that number is not what the Apple Watch app shows yet. Citing the paper does not turn the 40/25/20/15 marketing weights into PpgAge.

Nuvo’s 21 biomarkers are wearable plus optional conventional labs, recalculated daily on device. A HRV Works biological age and a Nuvo biological age on the same calendar day are answering different questions. One is “how do VO2 max, resting heart rate, sleep, and activity weight today.” The other is “how do 21 longevity biomarkers, including any lab PDF you added, weight today.”

Nuvo does not implement HRV Works’ four weights, meeting-stress prediction, or 10-year pace chart. HRV Works does not implement Nuvo’s 21-biomarker daily biological age.

Can they stack?

Yes, with a narrow overlap. Use HRV Works when you want the calendar layer: which meeting ran hot, whether last night’s habit showed up in recovery, whether the 60-day HRV baseline says to push. Use Nuvo for the daily 21-biomarker trend on HealthKit plus any conventional lab PDF you already have. Both can read Apple Health. Nuvo can also take Garmin or Oura through HealthKit. A lab PDF can sit in Nuvo’s score. It does not become HRV Works’ wearable composite, and HRV Works’ meeting prediction does not become a Nuvo biomarker.

They are partial substitutes if the only question is “give me a biological age from my Apple Watch.” They are complementary if you want calendar-stress coaching and a lab-capable 21-biomarker score. If you only want the schedule-and-HRV coach, stop at HRV Works — once you can install it. If you only want the daily 21-biomarker age, stop at Nuvo.

Privacy

Read both of HRV Works’ public documents. The homepage says processing is on-device and “your data never leaves your device,” next to a HealthKit footnote. The privacy policy effective 1 December 2025 says that if you sign in, they collect your email and an authentication token, store the email in their database, may collect anonymized usage statistics and crash reports, and use third-party services for database storage, authentication, and analytics. The terms say you may need an account for some features, that you grant a license to store and process data to provide the service, and that cloud services handle database storage and authentication. HealthKit is named as a permissioned source. We did not find an App Store privacy nutrition label that would show how Apple classifies the binary. Until a listing exists, the homepage sentence and the policy are unresolved against each other. We are not going to collapse them into “same privacy as Nuvo.”

Nuvo is no account, on-device Nuvo Intelligence, Data Not Collected, data not sent to Nuvo servers, not sold. Subscriptions bill through Apple. Architecture notes: health app privacy and on-device AI.

Where HRV Works wins

HRV Works wins if the job is calendar stress on Apple Watch. Meeting-stress prediction, a Context Engine tied to the calendar, habit impact, a live stress monitor, and a morning brief aimed at the schedule are the product. Nuvo does not claim that coaching surface. A 60-day HRV recovery score, body battery, and a 10-year aging-pace chart are also theirs to sell. If you came for “which meeting drained me,” buy that product when the beta — or a later App Store release — will actually install.

HRV Works also wins the early-tester story they choose to tell: the homepage prints 500+ beta testers. That is not an App Store rating corpus. Nuvo’s published US rating count is 4. We are not going to inflate four ratings, and we do not publish a schema.org rating object for Nuvo.

Where Nuvo wins

Nuvo wins on the daily biological-age job that can include labs. HRV Works’ public age is VO2 max, resting heart rate, sleep, and activity. Those update with wear. They do not fuse optional HbA1c, CRP, or HDL into a 21-biomarker clock. Nuvo recalculates a daily biological age from 21 biomarkers so sleep, HRV, training, and optional labs can sit in one number.

Nuvo wins on a price you can actually subscribe to in public. Both show a $4.99 monthly sticker. Nuvo also publishes $24.99/year after a 7-day trial. HRV Works’ homepage table lists monthly $4.99 only. We did not find a yearly price. Twelve times $4.99 is $59.88 if that monthly price is the only plan. An in-app annual discount could still exist that the website does not show. This page does not assume one. The documented annual price in this comparison is Nuvo’s.

Nuvo wins on being on the App Store. Nuvo: Longevity Coach (id 6762535065) is a public listing. HRV Works’ public download on the check date was a TestFlight link that was not accepting new testers, while the homepage still advertised the beta. A closed beta is not a substitute checkout.

Nuvo also wins on a privacy story that matches its policy: no account, Data Not Collected. HRV Works’ homepage and its privacy policy do not match each other. See the privacy section.

Who wins for which user

Choose HRV Works if you want Apple Watch calendar stress, HRV recovery coaching, habit impact, and a wearable biological age from VO2 max, resting heart rate, sleep, and activity — and you can get the build. Choose Nuvo if you want a daily 21-biomarker biological age on iPhone and Apple Watch, privately, at $24.99/year, with optional labs. Use both if you already have HRV Works for the calendar and still want a daily age number from HealthKit plus any conventional lab PDF you have. They do not compute the same age.

If the only job is “meeting stress and a Watch composite age,” stop at HRV Works. If the only job is “daily biological age from 21 biomarkers, privately, on iPhone,” stop at Nuvo. Download app.

Habits that actually move aging markers — sleep, aerobic fitness, glucose, inflammation — are covered in How to reduce biological age and lowering biological age with Apple Watch. This page is about which product does which job.

Pricing math without invented discounts

HRV Works, on the homepage table checked 15 October 2026: $4.99/month. No annual SKU on the homepage, privacy policy, or terms, and no App Store price list because we did not find a listing. The TestFlight page noted that beta subscription renewals are accelerated during testing; that is Apple’s TestFlight boilerplate, not a HRV Works price.

Nuvo: $4.99/month or $24.99/year ($2.08/month billed annually) after a 7-day trial. No mailed sample is bundled.

The monthly stickers match. The yearly price we can cite is Nuvo’s. The products still differ if the dollars were identical: calendar-stress coach plus a four-input wearable age, versus a 21-biomarker daily age that can include labs. Comparing $4.99/month HRV Works to $4.99/month Nuvo as if they bought the same object is a category error.

Related articles

• Nuvo vs Athlytic — Apple Watch Recovery, Exertion, and Athlytic Age versus a daily 21-biomarker score.
• SuperAge vs Nuvo — another Apple Watch biological-age app.
• Nuvo vs WHOOP — a strap’s strain and recovery, which HRV Works’ own table compares itself against.
• Nuvo vs Oura — a sleep ring rather than a Watch stress app.
• VO2 max and biological age — the input HRV Works weights at 40%.
• Apple Watch longevity tracking — the wider Watch field.
• Best biological age apps in 2026.

Frequently Asked Questions

Should I pick Nuvo or HRV Works?
Pick HRV Works if you want Apple Watch calendar and meeting stress, a recovery score against a 60-day HRV baseline, habit impact, body battery, and a wearable biological age from VO2 max, resting heart rate, sleep, and activity. The public price on their comparison table is $4.99/month, and the public download is TestFlight. Pick Nuvo if you want a daily biological age from 21 biomarkers on iPhone and Apple Watch, optional conventional lab PDF in that same score, on-device AI, no account, and $24.99/year after a 7-day trial. They are partial substitutes on “biological age” and complementary if you want both the calendar coach and the 21-biomarker score.

Is HRV Works a biological age app?
It markets one. The homepage biological-age card uses VO2 max, resting heart rate, and sleep quality, and the weights on that page add activity at 15%. That is a wearable composite. It is not Nuvo’s daily 21-biomarker biological age, and their own essay says the PpgAge research clock is not explicitly shown in the Apple Watch app yet.

How does HRV Works calculate biological age?
The homepage “How We Calculate Bio Age” section, checked 15 October 2026, lists 40% VO2 max, 25% resting heart rate, 20% sleep quality, and 15% activity level. The feature card shortens that to VO2 max, resting heart rate, and sleep quality. We did not find a methods paper that derives those four weights. The separate PpgAge essay discusses Miller et al., Nature Communications (2025), DOI 10.1038/s41467-025-64275-4, and says that model is not the number the Apple Watch app shows yet.

Does HRV Works include blood labs?
Not on the homepage, privacy policy, or terms we checked. The published age inputs are wearable: VO2 max, resting heart rate, sleep, and activity. Nuvo can take optional conventional lab PDFs into the same 21-biomarker score.

How much do HRV Works and Nuvo cost?
HRV Works’ public comparison table lists $4.99/month. We did not find a yearly price or an App Store in-app purchase list on 15 October 2026. Nuvo is $4.99/month or $24.99/year ($2.08/month billed annually) after a 7-day trial. Same monthly sticker; Nuvo is the one with a published annual price.

Is HRV Works on the App Store?
We did not find a public App Store listing on 15 October 2026. The homepage links to TestFlight (join/eeV49yQ8). That beta page said it was not accepting new testers. The homepage still described the beta as open and cited 500+ testers. Nuvo is on the App Store as Nuvo: Longevity Coach, id 6762535065.

Does HRV Works keep data on the device?
The homepage says yes: 100% on-device, data never leaves the device, HealthKit processed on-device. The privacy policy effective 1 December 2025 says sign-in email is stored in their database and that the app may use analytics, crash reports, and third-party database and authentication services. The terms name cloud storage. We did not find an Apple privacy nutrition label. Nuvo’s label is Data Not Collected, with no account.

Can I use Nuvo with HRV Works?
Yes. They are complementary for different jobs and partial substitutes if you only wanted one Watch-based age number. HRV Works is the calendar and HRV coach. Nuvo is the daily 21-biomarker readout on HealthKit plus optional lab PDFs. Nuvo does not ingest HRV Works’ biological age or meeting-stress score as a named input.

Does Nuvo require an account?
No. Nuvo uses on-device private AI and no account. Apple’s privacy label is Data Not Collected; data stays on the phone. HRV Works’ terms say some features may require an account, and the privacy policy describes storing sign-in email. Privacy is a difference, not a tie. The product difference is 21 longevity biomarkers (HealthKit plus optional labs) versus calendar stress plus a wearable age composite.

Is this medical advice?
No. This comparison is educational and is not medical advice. Neither HRV Works nor Nuvo replaces care, diagnosis, or treatment from a licensed clinician. Recovery scores, wearable biological age, aging-pace charts, and lab results should be reviewed with a qualified professional.

If the job is a daily biological age from 21 biomarkers on the iPhone and Apple Watch you already own, Download app.