Disclosure: I'm building one of the apps in this comparison (Haea). I've tried to be honest about where the existing options are strong and what gap I think Haea fills. If on-device privacy isn't a constraint, the analytics-rich cloud options (MyFitnessPal, Strava, etc.) may serve you better — this comparison is only about the privacy-first subset.
What "on-device" actually means
The phrase is overused in app marketing. For this comparison, "on-device" means: your health data is stored on your iPhone, never transmitted to the developer's servers, and any analysis happens locally. There are degrees: some apps are fully on-device (no network calls related to your data), others sync via Apple's CloudKit (still your iCloud, not the developer's). Both qualify; cloud-hosted health platforms (MyFitnessPal, Fitbit's app, most weight-loss services) do not.
Apple Health (built-in)
Cost: Free. Platform: iOS, comes with every iPhone.
Apple Health is the foundation. It collects sleep, steps, heart rate, HRV, workouts, weight, and a long list of other measurements either from the iPhone's sensors, from an Apple Watch, or from third-party apps that write into HealthKit. All of it is stored on-device with optional end-to-end encrypted iCloud sync.
Strengths: the most permissive integration target. Anything that integrates with HealthKit can read from and write to your Apple Health store. Full data export available. No third-party server involved.
Limitations: the analytics layer is thin. Apple shows trends and summaries but doesn't surface deeper patterns — no correlation between sleep and HRV, no circadian rhythm insights, no causal inference between nutrition and energy.
Bearable
Cost: Free tier + Premium ~$5/mo. Platform: iOS + Android.
Bearable is a symptom-tracking app aimed at people managing chronic conditions. The model is: track factors (sleep, food, mood, medication, weather) and symptoms over time, then surface correlations.
Strengths: excellent for chronic-condition tracking. Very flexible custom factor / symptom definitions. Correlation finder is genuinely useful for identifying triggers.
Limitations: data lives on Bearable's servers by default (with an export option, but cloud-first). Less helpful for general analytics — it's built around symptom triggers, not fitness/wellness patterns.
Welltory
Cost: Free tier + Premium ~$10/mo.
Welltory specializes in HRV-based stress and energy measurements via the iPhone camera or wearable integration. Daily measurements over time produce a stress + energy trend.
Strengths: HRV depth that Apple Health doesn't match natively. Daily measurement habit is easy.
Limitations: data is sent to Welltory's servers for analysis. The "AI coach" surface is cloud-based. Not on-device in the strict sense.
Haea (in development)
Cost: Free tier + Premium ($1.99/mo or $14.99/yr). Platform: iOS 17+. Status: 2026 expected launch.
Haea is the app I'm building to fill what I think is a missing position: a deep-analytics health app where the analysis is fully on-device. Reads from Apple Health (HealthKit), processes everything locally, surfaces patterns through Kalman-filtered weight smoothing, TDEE calculation, circadian rhythm modeling, Granger causality between factors, and a one-line morning summary.
Why a new entry: the existing options force a trade-off. Apple Health is on-device but the analytics are basic. Bearable and Welltory have richer analytics but require cloud sync. Haea aims to give you both — the analytical depth of a paid health platform with the privacy posture of Apple Health, without compromise.
How "on-device" is verifiable for Haea: the app makes zero network calls related to your health data. The only network activity is the in-app purchase flow (Apple's, not ours) and a possible launch crash-report payload (anonymized, no health data). The architecture is observable in the app's network behavior.
Quick comparison
| App | Where data lives | Analytics depth | Best for |
|---|---|---|---|
| Apple Health | iPhone + iCloud (yours) | Basic | Baseline data collection |
| Bearable | Bearable servers | Symptom correlations | Chronic condition tracking |
| Welltory | Welltory servers | HRV / stress | Daily stress measurement |
| Haea (2026) | iPhone only | Deep (ML-based) | Privacy-first analytics |
How to choose
- You just want Apple's baseline collection: Apple Health is already on your iPhone. Use it. Many users will get 80% of the value without installing anything else.
- You're managing a chronic condition and want to find triggers: Bearable.
- You care specifically about HRV and stress: Welltory (accepting the cloud trade-off).
- You want deep analytics without leaving your phone: Haea (when it launches in 2026).
For more on why on-device matters specifically for health data, see Why we built Haea on-device. For the full privacy posture across all Purplelink apps, see the privacy policy.