Heart rate is a primary metric for the physiological load someone is under. The following products can be used to capture, process or distribute heart rate data. More advanced wearable devices can also capture more, including breathing and motion.
Heart Rate Sensor Strap
Dual-mode (ANT+ and BluetoothLE/BLE) heart rate strap
Heart Rate Wrist Sensor
Wrist-worn heart rate sensor with BluetoothLE/BLE and/or ...