How do I pair a power meter, heart-rate monitor, or trainer?

Open Settings → Connections. Check the Bluetooth status, wake up your sensor, then tap Scan and choose the device you want to connect.

The app supports power, speed/cadence, and heart-rate sensors over Bluetooth LE, and compatible smart trainers or smart bikes over Bluetooth FTMS. An ANT+-only sensor needs Bluetooth-capable hardware or a bridge to work with an iPhone.