Breathing generator

Breathing is a motion that never stops for long - unless you are dead of course. Put an elastic belt around your chest that has built in Piezo elements or some other generator in a suitable configuration and you make power from breathing, even in your sleep. It won't be a lot of power since you don't want nightmares about being strangled by a python, but it could probably keep a cell phone charged or run a heartbeat monitor, or other useful widgets. The device could also help to burn extra calories for those who need it.