Nokia has applied for a patent that will charge your phone while you walk. It sounds similar to those self winding watches that renew their energy as you swing your arms. Certain components inside the phone are on a movable frame that moves up and down or side to side depending on your motion. This is the basis for energy generation.It goes by the snappy name "Piezoelectric Kinetic Energy Harvester." They are going to have to come up with something that rolls off the tongue a bit easier if this ever makes it to market. The basic operation is summarized in the patent abstract:

That is a little dry, as patents tend to be, but it sounds like they are putting as much weight as possible in this moving tray. The more weight there is, the more potential energy there is to convert to electricity as the user moves around.

The idea sounds interesting but I'll be curious to see how they pull this off without two negatives that come to mind. First of all, for all of this motion to happen, there has to be a certain amount of space in the device, which means the shell is larger than it otherwise needs to be. The second problem is how does it feel to have this in your pocket with internal components sloshing around? It makes me think of those times when I used to carry around a handheld transistor radio that had the 9 volt battery rattling around inside.

I wonder if anyone is working on a phone that charges by drawing energy from the motion of the jaw while the user talks? At least teenaged girls' phones would never run out of juice.