Apple Watch heart rate reaches the iPhone through a mirrored workout.
That detail matters. The iPhone is not secretly reading the Watch sensor whenever it wants. The Watch starts a workout, HealthKit mirrors that session, and Zonas shows the mirrored state on iPhone.
How To Use It
- Install Zonas on iPhone and Apple Watch.
- Open Zonas settings on iPhone.
- Select
APPLE WATCHas the source. - Start the workout from the Watch flow.
- Keep the Watch workout running.
- Open Zonas on iPhone to see the mirrored workout state.
- Enable Live Activity or Picture-in-Picture if you want an always-visible phone surface.
The Watch remains the source of heart rate.
What Happens Under The Hood
The Watch starts an HKWorkoutSession.
The Watch attaches a live workout data source, receives heart rate from Apple Watch sensors, calculates the current zone, and mirrors the session to iPhone.
The iPhone accepts that mirrored session and displays:
- workout type
- elapsed time
- current heart rate
- current zone
- stale-data status if updates stop
Why This Is Better Than Polling
Apple Watch is not a standard BLE heart rate strap from the iPhone’s point of view.
The supported Zonas path is a companion Watch workout. That lets the Watch own the sensor session and lets the phone show the result.
It is less magical than “just read the Watch.” It is also more honest.
Display Options On iPhone
Once the mirrored workout is active on iPhone, Zonas can use the same display surfaces as a BLE workout:
- in-app workout screen
- Live Activity
- Dynamic Island
- Lock Screen
- Picture-in-Picture
Live Activity and Picture-in-Picture are separate controls in the workout UI.
If Updates Stop
If the iPhone stops receiving Watch heart rate updates, check the simple things:
- the Watch workout is still running
- the Watch app is open or active
- the devices are near each other
- Health permissions are allowed
- the Watch has a good heart rate reading on wrist
Zonas can warn when Watch data looks stale.
Common questions
Does the iPhone pull heart rate from Apple Watch in the background?
No. Zonas uses a Watch companion workout and HealthKit session mirroring. The Watch owns the workout and sends live data to the companion iPhone app.
Can I start from the Watch?
Yes. The Watch app can run the workout and mirror it to iPhone. The iPhone then shows the active workout state.
What if heart rate stops updating on iPhone?
Open the Watch app and keep the workout active. Zonas can show a stale-data warning when Watch heart rate messages stop arriving.
Sources
- Monitor your heart rate with Apple Watch
Apple Watch measures heart rate continuously during workouts.
- startMirroringToCompanionDevice
watchOS workout sessions can mirror to the companion iOS app.
- Displaying live data with Live Activities
The mirrored heart rate can be displayed on iPhone surfaces such as Lock Screen and Dynamic Island through Live Activities.