Scientists have developed and implanted into a living insect — the False Death‘s Head Cockroach — a miniature fuel cell that converts naturally occurring sugar in the insect and oxygen from the air into electricity. They term it an advance toward a source of electricity that could, in principle, be collected, stored and used to power sensors, cameras, microphones and a variety of other microdevices attached to the insects in a paper in the Journal of the American Chemical Society.
http://www.physorg.com/news/2012-02-biofuel-cell-electricity-implanted-false.html