There is an old thread on this in the archives.  basically,
you need a 1-inch piezo speaker element, a diode, and a cap,
and you support the piezo between a couple of pieces of
flexible plastic, and put it in the heel of your shoe.  i
dont remember that anyone reported results--i have the parts
in a ziplock but never tried it.
alice

> I find these alternate energy threads fascinating,
> especially due to the latest ransom we've been expected
> to pay at the pumps!!!
>
> Someone mentioned generating a watt of power from stressing
> a crystal.  Can someone offer a practical procedure where
> one could start experimentation with this.
>
> Just think of a flashlight where one could hammer on it to
> make it work.  This is what we do anyway when the bulb goes,
> but with white leds, not a problem anymore.
>
> Technological advancement; got to love it!
>
> Craig