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:

A battery for an electronic device is contained within a first frame that is coupled to a second frame by one or more piezoelectric elements. The second frame is coupled to a device chassis by one or more additional piezoelectric elements. In response to translation and/or rotation of the electronic device, portions of forces induced by the battery mass are transferred to the piezoelectric elements. Electrical energy output by these piezoelectric elements is received in a power controller and can be applied to the battery. Additional device components can also be contained within the first frame so as to increase the total mass that induces forces applied to the piezoelectric elements.

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.