It has been oft said that if we could harness the power of endlessly talking, we could solve all the world's energy problems.
Well, I don't know about all that, but here's an idea that takes a step towards it: I've seen wristwatches that wind themselves everytime your wrist moves, using some sort
of
sliding mechanism (I have no idea exactly how it works, so I won't get into the technical aspects of this idea). In fact, I had a Steinhausen watch that wound itself like that.
Why not design a headset that has a chin strap with the same sort of mechanism so that everytime your jaw moves when you speak, it charges a little generator which in turn charges your cell phone via wire? This would supplement the battery's output enough to dramatically increase your talk time.
Now, I realize that the headset may look a little unfashionable, and there's really no actual need to put the charging device on a headset. It could be attached to a wristband or attached to your leg so it charges while walking. Either way, I see no reason we can't use the motion of the body to power something that small.