I've got this - and found out that it's basically quite easy. It just goes off the first time you move within the 1/2 hour time slot of your set alarm time.
It's quite good, but now I just try to not move in the morning, so that the alarm doesn't go off.

The statistics are quite interesting to begin with, and I do like the alarm sounds, from quiet to louder. I have the urban sound set up and it's much better than a shrill beeping. Unfortunately, Mr C stills relies on the beep, so we get the best of both worlds.