HappyWakeUp, sound motion detection

This HappyWakeUp application looks cool, it would definitely be better to be able to keep the phone near your pillow instead of on your wrist.. and sense sound instead of motion..
If the sensitivity of the mic is good enough, it can monitor your motion all through the night..
But having it ringing when you move within the last 20 minutes is an oversimplification of the concept..
Anyway, and according to Daniel, it would not be useful in the case of two (or more) persons in the room.. and it is liable to different noises from around.