Fitness apps lose users over numbers they don’t believe
If your reviews ask for watch sync, or complain about wrong step counts, missed morning workouts and streaks broken by timezone bugs, we can fix that. We build wearable integrations at $3,500 per platform, with deduplication, background delivery and the edge cases handled.
Why sync breaks
The four failure modes behind every “sync is broken” review
These are the four reasons simple sync implementations fail in the field.
Background delivery isn't guaranteed
iOS and Android both throttle background wake-ups aggressively. A sync that only runs when the app opens misses the morning run logged at 6 am, and the user notices before you do. A correct implementation combines background delivery, anchored queries and reconciliation when the app comes to the foreground, so data arrives even when the OS held it back.
Duplicates from multiple sources
A user with an iPhone and an Apple Watch reports the same steps twice. Add a Garmin, and a workout exists in three places with three calorie counts. Without source-priority and merge rules, your app confidently displays wrong numbers, and data-driven users leave over it.
Units, timezones and midnight boundaries
Unit conversion is simple; day boundaries are not. A workout logged at 11:50 pm in one timezone and synced at 7 am in another has to land on the right day for your streak feature. Get it wrong and a user loses a 200-day streak, which usually ends up in a review.
Permission flows that silently fail
Health permissions are granular, revocable and easy to get into a half-granted state. Users deny one scope, upgrade their OS or reinstall, and sync stops without an error. A well-built integration detects the state, explains it in the app and recovers, instead of showing a blank where the heart rate should be.
Platform coverage
Six platforms, each treated as its own project
Apple HealthKit
The default for iOS fitness & wellness apps
On-device store, background delivery, granular per-type permissions. App Review has specific rules for health data, and we build to them.
Google Health Connect
Android's unified health layer (with Google Fit sunset)
The successor to Google Fit's APIs. One integration reaches Samsung Health, Fitbit and more on Android, and migration from legacy Fit is included.
Garmin
Runners, cyclists and triathletes, often your most data-obsessed users
Cloud API with webhook pushes, detailed activity files and training metrics. These users spot sync errors first.
Whoop
Recovery- and strain-focused training audiences
Cloud API for recovery, strain, sleep and workouts. Ideal for coaching platforms that program around readiness.
Fitbit
A large mainstream base, especially in corporate wellness
OAuth cloud API for steps, sleep and heart rate. Rate limits cap how often you can sync, so we design the sync schedule around them and tell you what users will see.
Oura
Sleep-first wellness and recovery products
Clean cloud API for sleep stages, readiness and HRV. Often the fastest integration to ship.
The scope, in full
What a $3,500 integration includes
$3,500 covers one platform and all five deliverables below. It isn’t billed hourly, and nothing that belongs in the first build is pushed to “phase two.”
Integration design
Which data types, which direction and how they merge into your existing model, plus the source-priority rules that keep the numbers right when a user owns three devices.
Implementation
Auth and permission flows, sync engine, background delivery, webhook handling, unit and timezone normalization. It is production code in your codebase, not a black-box SDK wrapper.
Edge-case handling
Duplicates, revoked permissions, offline gaps, backfilled history, DST transitions and the midnight-boundary problem. This is a large share of the work, and it decides whether users trust the sync.
QA on real devices
Tested against physical watches, rings and phones as well as sandbox data. We exercise background scenarios, permission-denial states and multi-source accounts before your users hit them.
Documentation & handoff
How the sync works, the merge rules, the failure states and how to observe them, written down so your team can maintain the integration long after the people who built it have moved on.
Already have a flaky integration? We assess what exists before quoting, and if it’s repairable, you pay for the repair, not a rebuild.
Get my sync assessedCommon questions
Wearable integration FAQ
Why $3,500 per integration instead of one price for all of them?
Because each platform is its own project. HealthKit is an on-device framework with background delivery quirks; Garmin and Whoop are cloud APIs with their own auth, webhooks and rate limits; Health Connect changed Android's model entirely. Per-integration pricing means you pay only for the platforms your users have, and each one is delivered complete.
Which integration should we build first?
The one your reviews and support tickets are asking for. If that's unclear, your user analytics settle it. As a general pattern, iOS-heavy consumer fitness apps start with HealthKit, Android with Health Connect, endurance-sport audiences skew Garmin, and recovery-focused products skew Whoop and Oura.
Our current sync sort of works but users complain about wrong numbers. Rebuild or repair?
Usually repair. “Wrong steps” is most often a deduplication problem (phone and watch both reporting), “missed workouts” a background-delivery problem, and “numbers changed overnight” a timezone problem. We assess the existing implementation first, and if the foundation is sound you pay only for the fix.
Do you handle the health-data privacy side?
We implement the platform requirements (permission flows, scoped read access, store-review rules for health data) and design the architecture so wearable data lives in known, deliberate places. Formal privacy compliance (HIPAA, GDPR assessments) is a separately qualified scope: we build to the boundary your privacy specialists define, and we agree that split from day one.
How long does an integration take?
Typically two to four weeks per platform, depending on how your data model needs to absorb it. The API wiring is the fast part; the merge rules, unit normalization and QA on real devices take most of the calendar.
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Give your users numbers they can trust
Send us your stack and a few of the reviews that mention sync. We'll recommend which integration to build first and scope it.