Fitness app build plan and PRD generator
Pick the app type, platforms, data sources and features, and this generator writes a build plan you can share as a link or download as Markdown: an architecture outline linking the page that covers each layer, the products from this site's cost model that fit, the cost shape (how each product bills and our labeled effort judgment, never a price), the health-data rules your answers point to, and the store-review items that apply. The same answers fill a PRD template that quotes Apple's and Google's documentation on edge cases such as HealthKit read denial and Health Connect's 30-day read window. It is a starting plan, not legal advice.
Sources read 2026-11-05. Not legal advice.
Build plan: Sleep tracking app
Build guide: Sessions That Cross Midnight and Devices That Disagree in Sleep Tracking Apps
Architecture outline
- iOS app reads and writes HealthKit on the device: Apple HealthKit Integration Guide (2026), HealthKit Queries
- Android app reads and writes Health Connect on the device: Health Connect API Integration Guide (2026), Health Connect API
- Phone-to-backend sync from the on-device store: Incremental Sync: Reading Only What Changed Since Last Time, Background Sync That Does Not Depend on the Phone Waking Up
- Cloud ingestion: user authorization, webhooks and history backfill: Mapping Users to Wearable Provider Accounts and Devices, Webhook ingestion for health data: making at-least-once delivery safe, Backfilling Years of Wearable Data Without Hitting Rate Limits
- Normalize, deduplicate and bucket by the user's day: Normalizing wearable data across providers, Deduplicating Health Data From Multiple Sources, Timezones and Day Boundaries: Whose Midnight Defines the Day?
- Storage, gaps, deletion and export: How Should You Store Health Time-Series Data?, Missing Data and Gaps in Health Metrics, Deleting and Exporting a User's Health Data
Health data types this app type touches
| HealthKit | Aggregate with | Health Connect |
|---|---|---|
| sleepAnalysis | not stated by Apple | SleepSessionRecord (carries stages) |
| restingHeartRate | discrete | HeartRateRecord, RestingHeartRateRecord |
| heartRateVariabilitySDNN | discrete | HeartRateVariabilityRmssdRecord |
| respiratoryRate | discrete | no verified pair |
| oxygenSaturation | discrete | OxygenSaturationRecord |
| appleSleepingWristTemperature | discrete | no verified pair |
| appleSleepingBreathingDisturbances | not stated by Apple | no verified pair |
Products that fit (8)
| Product | How it bills you | Approval gate | Effort (our judgment) |
|---|---|---|---|
| Apple HealthKitPlatform health stores · in the build guide | Free | App Store review checks that your health usage-description strings match what you actually do. | medium |
| Fitbit Web API (Google)Wearable APIs (direct) · in the build guide | Free | Developer app registration; access to other users' intraday data is case-by-case (verify). | medium |
| Garmin Health / Activity APIWearable APIs (direct) · in the build guide | Free | Garmin Connect Developer Program approval, as Starter or Enterprise Access; Garmin's pages state no review time. | high |
| Google Health ConnectPlatform health stores · in the build guide | Free | Play Console health-data declaration and review before you can publish. | medium |
| Oura Cloud APIWearable APIs (direct) · in the build guide | Free | A new API application is limited to 10 users until Oura approves it, with no limit once approved. | medium |
| WHOOP Developer PlatformWearable APIs (direct) · in the build guide | Free | New apps start on a Sandbox tier of 10 members and move up through reviewed tiers of 100, 1,000, 5,000 and unlimited; developers need a WHOOP membership to build. | medium |
| Polar Open AccessLinkWearable APIs (direct) | Free | None recorded | low |
| Strava APIWearable APIs (direct) | Free | A Strava subscription is a prerequisite for creating an app, which starts in single-player mode; a self-service upgrade raises its athlete capacity to 10, and connecting more than 10 needs Strava's review. | medium |
Cost shape
- Free: Apple HealthKit, Fitbit Web API (Google), Garmin Health / Activity API, Google Health Connect, Oura Cloud API, WHOOP Developer Platform, Polar Open AccessLink, Strava API
- Integration effort per product: from low to high. Integration effort is this site's rough judgment, not a vendor fact: low is roughly days, medium roughly weeks, high roughly months.
- No prices, on purpose: the cost model records how each product bills, not what it charges today.
Compliance: what likely applies
- HIPAA (neither a covered entity nor a business associate): Likely does not apply. On your answers you are neither a covered entity nor acting for one, so HIPAA likely does not reach the app. Other rules below still can.
- FTC Health Breach Notification Rule: Likely applies. A health or fitness app outside HIPAA is the case the FTC says its breach rule covers.
- FTC Act: what you claim about privacy: Likely applies. Whatever HIPAA's answer, the FTC tells health-app makers not to claim HIPAA compliance or certification they do not have.
- FDA: general wellness or medical device: Likely does not apply. Software only for maintaining or encouraging a healthy lifestyle is outside the device definition, per the provision the FDA quotes below. Medical claims change that.
- Apple App Review Guidelines: Likely applies. You ship on iOS. The App Store's health rules apply to every health and fitness app there.
- Google Play Health apps and Health Connect policies: Likely applies. You ship on Android. Google Play's Health apps policy applies to any app with health features.
Open these answers in the compliance wizard, with each rule quoted →
Store submission
33 checklist items apply (Apple App Store and Google Play). Open them in the store submission checklist →
Edge cases the platforms document
- A denied HealthKit read looks exactly like no data
To help prevent possible leaks of sensitive health information, your app cannot determine whether or not a user has granted permission to read data. If you are not given permission, it simply appears as if there is no data of the requested type in the HealthKit store. (Apple)
- Health Connect reads stop at 30 days before the first grant
By default, all applications can read data from Health Connect for up to 30 days prior to when any permission was first granted. (Android Developers)
- Older history needs its own permission
Otherwise, without this permission, an attempt to read records older than 30 days results in an error. (Android Developers)
- An unused Health Connect changes token expires
Since an unused Changes token expires within 30 days, you must use a sync strategy that avoids losing information in such a case. (Android Developers)
- Google Fit is not a foundation to build on
The Google Fit API (including the REST API) will only be supported until the end of 2026. (Android Developers)
Where each part of the plan comes from
- App types and health data types: the build guides and the concrete stack each one names, joined to Apple's identifier dataset and, for Android, only to pairs both platforms' documentation confirms.
- Products and the cost shape: the provenance-tracked model behind the cost planner and the API directory, which records how each product bills, what each user must own and which approval gates a launch, and states no prices.
- Compliance: the quoted rules of the compliance wizard, routed from your answers.
- Store review: the items of the store submission checklist that your platforms and features trigger.
- Architecture: one line per layer, each linking the page on this site that covers it, from on-device sync to deletion and export.
What it will not do
It will not price the plan. The cost model behind it holds no dollar figures, because most serious tiers in this market are contact-sales and public prices move; the plan groups products by how they bill and gives the span of our effort judgment (low is roughly days, medium roughly weeks, high roughly months), labeled as ours.
It will not rank. Products the build guide for your app type already names sort first, then by how they bill; nothing is scored. KinesteX, which funds this site, appears only in a plan that includes camera motion tracking, and then with the disclosure beside it.
It will not decide your legal position. The compliance section is a routing from your answers to rules quoted from their sources; the compliance wizard asks the questions that settle HIPAA status, and a qualified professional should confirm the result.
The edge cases the PRD template quotes
The PRD's edge-case section quotes the platforms' own documentation for the platforms you pick, read on November 5, 2026:
- A denied HealthKit read looks exactly like no data: “To help prevent possible leaks of sensitive health information, your app cannot determine whether or not a user has granted permission to read data. If you are not given permission, it simply appears as if there is no data of the requested type in the HealthKit store.” (Apple, authorizationStatus(for:))
- Health Connect reads stop at 30 days before the first grant: “By default, all applications can read data from Health Connect for up to 30 days prior to when any permission was first granted.” (Android Developers, Read raw data (Health Connect))
- Older history needs its own permission: “Otherwise, without this permission, an attempt to read records older than 30 days results in an error.” (Android Developers, Read raw data (Health Connect))
- An unused Health Connect changes token expires: “Since an unused Changes token expires within 30 days, you must use a sync strategy that avoids losing information in such a case.” (Android Developers, Synchronize data (Health Connect))
- Google Fit is not a foundation to build on: “The Google Fit API (including the REST API) will only be supported until the end of 2026.” (Android Developers, Google Fit migration guide)
Related planners
For the stack alone, the stack generator narrows a build guide's products with four questions. For a starting recommendation before you know the app type, the API picker asks three. If you would rather not write code, the no-code fitness app guide covers the builder platforms.
Next step
Turning this into a choice of API:
A free tool from AIFitnessAPI. More at free tools for health-app builders.