GymKit#
GymKit is Apple’s protocol for direct, bidirectional data exchange between Apple Watch and certified gym equipment. In this setup it connects the Apple Watch Ultra 1 directly to the Peloton Bike+ — no bridge device is needed.
In the Network#
| Link | Direction | Data |
|---|---|---|
| Peloton Bike+ → Apple Watch Ultra 1 | Equipment → Watch | Cadence, output (watts), calories, distance |
| Apple Watch Ultra 1 → Peloton Bike+ | Watch → Equipment | Heart rate |
This is the only protocol in this setup where the Watch receives real-time performance data directly from the source rather than through a bridge. On the outdoor bikes, Watchlink translates ANT+ sensor data to Bluetooth LE for the Watch; GymKit eliminates that intermediate step entirely.
Key Characteristics#
| Attribute | Spec |
|---|---|
| Underlying transport | Bluetooth LE |
| Direction | Bidirectional (equipment ↔ Watch) |
| Connection initiation | Watch detects compatible equipment; tap Watch to equipment NFC tag or select from Watch |
| Apple Watch requirement | Series 1 or later |
| Equipment certification | MFi (Made for iPhone/iPad/Apple Watch) — manufacturer must be Apple-certified |
| Workout recording | Automatic — Watch opens and closes a workout session tied to the equipment session |
How the Connection Works#
- The Apple Watch Ultra 1 detects nearby GymKit-compatible equipment over Bluetooth LE
- The Watch prompts to connect (or the user taps the Watch to an NFC tag on the equipment)
- A secure pairing session is established directly between Watch and equipment — the iPhone 16 Pro Max is not involved
- The equipment streams cadence, output, and other metrics to the Watch in real time
- The Watch streams heart rate back to the equipment
- When the Peloton class ends (or the user manually stops), both devices close the workout simultaneously
- The completed workout syncs from Watch to iPhone Health app
Why GymKit Exists#
Without GymKit, a Watch user on a Peloton would have to:
- Manually start a workout on the Watch
- Trust the Watch’s wrist-based motion sensing to estimate indoor cycling metrics (inaccurate — no GPS, and wrist motion doesn’t correlate well to pedalling)
- Miss the equipment’s calibrated power, cadence, and calorie data entirely
GymKit eliminates this by giving the Watch a direct line to the equipment’s own sensors, which are far more accurate for indoor cycling metrics than Watch motion inference.
Comparison with the Outdoor Bike Setup#
| Aspect | Outdoor (ANT+ + Watchlink) | Indoor (GymKit) |
|---|---|---|
| Protocol chain | Sensor → ANT+ → Garmin → ANT+ → Watchlink → BLE → Watch | Equipment → BLE → Watch (direct) |
| Bridge device required | Yes (Watchlink) | No |
| Data source | Favero Assioma Pro MX (power), Shimano GRX Di2 (gear), etc. | Peloton Bike+ built-in sensors |
| Heart rate to display | Via Garmin Edge MTB (paired HR sensor) | Watch → Peloton (reversed direction) |
| Workout recording | Garmin Edge .fit file + Watch independently | Peloton + Watch simultaneously (synchronised) |
Equipment Supporting GymKit#
GymKit requires manufacturer certification from Apple. The Peloton Bike+ is one of the more widely known implementations. Other brands with GymKit support include Life Fitness, Matrix, Technogym, and Schwinn (select models). The original Peloton Bike (non-plus) does not support GymKit.