The health App on your phone will show you a graph of the times your watch has measured your heart rate. I have the Health App show me the graph under dashboard. The watch will attempt to measure your heart rate every 10 minutes - except if it senses you are moving or your arm is moving. For me (I have heart failure and I am prone to tachycardia events which can strike at anytime) I find the monitoring works well for me. It of course will also monitor your heart rate during a work out - using the workout app.
Hope this helps.
Stevi