6 min read
'No Data' Means Four Different Things
An empty health read has several causes and only one is 'connect your device'. Here is the order to rule them out before you write that empty state.
healthkithealth-connectarchitecture
Blog
Product breakdowns, API deep-dives, and playbooks for builders in health, wellness, and fitness tech.
What is actually in HealthKit
Counted out of Apple's own documentation, not from memory.
7 min read
HRV: Apple Watch SDNN vs Health Connect RMSSD
Apple Watch records HRV into HealthKit as SDNN; Health Connect stores RMSSD. Different statistics, no conversion factor, one chart that quietly misleads.
healthkithealth-connectdata
7 min read
Apple's Newest HealthKit Types Are a Roadmap
Apple ships the data type years before most apps ship the feature. The additions since iOS 16 are a public preview of what the platform expects to matter.
healthkitiosecosystem
6 min read
The HealthKit Error That Never Fires
HealthKit defines 17 error cases. The authorization-denied one is documented for saving, not reading — which is why an empty read is so hard to debug.
healthkitiosapi
7 min read
58 HealthKit Types Apple Never Explains
58 of HealthKit's 240 identifiers carry zero words of discussion prose, and the median across all 240 is 15 words. What to do when the docs say nothing.
healthkitdatamethodology
8 min read
HealthKit: 127 of 240 Types Are iOS 8.0
HealthKit has 240 type identifiers and 127 shipped in iOS 8.0. Four are deprecated, none removed. The full version histogram, and what it costs you.
healthkitiosdeprecation
Where the two platforms disagree
The places an Apple type and an Android record stop meaning the same thing.
7 min read
Health Connect SDK: 32 Releases, One Stable
Google has shipped 32 connect-client releases since August 2022 and one stable build, 1.1.0. The alpha runs, gaps and cadence, counted from the notes.
health-connectandroidecosystem
7 min read
Health Connect Has 219 Permissions
118 of Health Connect's 219 framework permissions are symptom strings added at API level 37. Read vs write, medical, background and history, counted.
health-connectandroiddata
What the APIs really cost
Approval gates, engineering effort, and the bill your users pay.
6 min read
The Fitness API Cost Your Users Pay
5 of 24 products bill your end user, not you. All five are direct wearable integrations, and the hardware requirement, not your budget, sets your reach.
wearablescostapi
6 min read
Four Ways an API Says Contact Sales
4 of 24 products list contact-sales, and their gate text describes four different waits. What to ask for, and what to have ready before the call.
costapiecosystem
6 min read
12 of 24 Fitness APIs Have an Approval Gate
Half the directory makes you get approved before production, and the gates are six different obstacles. Which ones start clocks you cannot compress.
apiecosystemcompliance
Everything else
2 min read
Welcome to AIFitnessAPI
Why we're building a hub for the people shipping the next generation of health, wellness, and fitness products — and what you can expect to find here.
announcementshealth techcommunity
3 min read
How to Choose a Fitness API in 2026
A practical framework for evaluating fitness and workout APIs: exercise data, motion tracking, AI coaching, pricing, and the questions that matter.
fitness APIguidesproduct