MotiFIT Run / Ride on Apple Watch has two basic modes of operation (ACTIVE WATCH MODE and PASSIVE WATCH MODE).
ACTIVE WATCH MODE
MotiFIT Run / Ride enters ACTIVE WATCH MODE when the workout is started directly from the Apple Watch. In this mode, MotiFIT Run / Ride runs natively on Apple Watch. The heart rate is read directly from the Apple Watch sensor.
Please note that for GPS tracking on the Apple Watch Series 1, a connection to the host iPhone is required during the workout. The built-in GPS features of the Apple Watch Series 2 allow you to use the Apple Watch to record GPS data without having an active connection to the host iPhone.
OPTIONAL: It is possible to pair an external Bluetooth heart rate monitor (Polar H7, Wahoo TICKR or Scosche Rhythm+) directly with your Apple Watch. It is recommended to turn off your iPhone's Bluetooth radio and then go to SETTINGS > BLUETOOTH on Apple Watch in order to pair the Bluetooth heart rate sensor with your Apple Watch.
PASSIVE WATCH MODE
MotiFIT Run / Ride enters PASSIVE WATCH MODE when the workout is started on the iPhone. In this mode, if you want to have heart rate readings, an external bluetooth heart rate monitor like a Polar H7, Wahoo TICKR or Scosche Rhythm+ needs to be paired with your iPhone to provide MotiFIT Run / Ride with heart rate samples.
Your Apple Watch simply mirrors the information gathered by MotiFIT Run / Ride running on your iPhone in this mode.