http://news.bbc.co.uk/1/hi/technology/6272752.stm

Good vibes power tiny generator

A tiny generator powered by natural vibrations could soon be helping keep heart pacemakers working.
Created by scientists at the University of Southampton, the generator has been developed to power devices where replacing batteries is very difficult.

The device is expected initially to be used to power wireless sensors on equipment in manufacturing plants.

The generator's creators say the generator is up to 10 times more efficient than similar devices.
The tiny device, which is less than one cubic centimetre in size, uses vibrations in the world around it to make magnets on a cantilever at the heart of the device wobble to generate power.

Although the generator produces only microwatts this was more than enough to power sensors attached to machines in manufacturing plants, said Dr Steve Beeby, from the University of Southampton, who led development of the device.
This is really neat. While the power generated is small, the future applications are vast.