OK, I haven't actually built any of this, and at this time I have no plans to, but sometimes when the straight line is handed to you, you gotta run with it.
Bayou Rennaisance Man notes this technological gem from England:
A vibrator that you recharge the batteries in by winding the crank, which the inventor suggests will be popular in the third world where batteries are scarce. Bayou has some familiarity with the third world, and suggests this will be a non-starter there, but let's keep thinking;
Here is a flashlight that gets its power from a shaking action that shuttles a magnet through coils inside:
No batteries at all, and it gets its energy from simple reciprocal shaking action. The perfect power source for the first device, no?
I'm calling my patent attorney. I believe I've just invented perpetual motion. Or solved the energy crisis. Or won a Nobel. Or something.
Or perhaps we should file this under "reasons why engineers should never be unemployed".