The problem
Apple Watch indoor-running distance can diverge from the distance measured by the treadmill belt, weakening the accuracy of saved training data.
The bet
If treadmill distance remains canonical while Apple Watch contributes heart rate and workout context, the combined record can be more accurate without losing the benefits of either device.
What I built
The native iPhone and Watch apps handle Bluetooth restoration, disconnect and reconnect catch-up, splits, pause and resume, HealthKit persistence, retries, and duplicate protection.
My role
I learned the FTMS hardware protocol, defined a single source of truth for distance, coordinated iPhone and Watch workout state, tested failure modes, and validated the output against a physical treadmill and Apple Fitness.
Where it stands
- My first Bluetooth and hardware project
- Validated against a LifeSmart TM4500 treadmill and Apple Fitness
- Treadmill distance stays canonical across disconnects and reconnects
- I use it several times a week