Tracking habits from Apple Health without opening an app

The most reliably completed habit is the one you never have to log. If your tracker reads step count from HealthKit, “walk 8 000 steps” fills itself in whether or not you remember the app exists, and your completion rate stops measuring your memory and starts measuring your behaviour.

HealthKit exposes a lot: steps, distance, active energy, exercise minutes, workouts by type, sleep stages, mindful minutes, weight, and a long list of clinical types most trackers ignore. A habit app can subscribe to any of them and write a daily value without a tap.

The caveat is data quality, and it varies enormously by metric. Step count from a phone in your pocket is good. Step count on a day you left the phone on a desk is a fabrication. Sleep from a Watch is decent, sleep inferred from phone usage is a guess. Workout minutes depend entirely on whether you remembered to start the workout, which puts you back where you started.

This guide goes metric by metric, says which ones are worth wiring to a habit and which are not, explains what read permissions actually grant, covers what happens on days with two sources of the same data, and shows how to combine an automatic metric with a manual one so the record stays honest.

Outline

Status: outline. The introduction above is finished copy. Everything below is the section plan for the full draft, targeted at about 1 900 words.

1. What HealthKit exposes. The metric families, and the ones a habit tracker can actually use.
2. Trustworthy by metric. Steps, sleep, workouts, mindful minutes and weight, rated with the failure case for each.
3. Permissions, plainly. What read access grants, what it does not, and how to audit it later.
4. Duplicate sources. Phone plus Watch plus a third app, and which number wins.
5. Setting a target that survives a bad day. Thresholds for automatic habits, and why they should be lower than you think.
6. Mixing automatic and manual. One habit filled by Health, one by hand, in the same list.
7. Privacy. Health data leaving the device, and how to check whether it does.