Do I have to keep my mobile device close while recording?
You can keep your mobile device with you while riding if you want to see your data in real-time. However, you do not have to!
You need to keep your device close to the sensor when starting and stopping a training session. Once the session started, you can leave your sensor in a corner of the arena, in your first aid kit, or elsewhere.
When you finish your session, take your mobile device, remove the sensor from the case and wait until they reconnect (in case the connection was lost). Once the blue light appears, you can stop your session.