An enzyme in the cockroach implanted biofuel cell breaks down sugars in the digestive tract, to form two simpler sugars called monosaccharides. Then a second enzyme oxidizes the monosaccharides resulting in the release of electrons.
The power isn't much at around 100 microwatts, but it may lead to a power source for tiny embedded electronics that turn the cockroaches into mini espionage cyborgs. All they need now is a way to steer the cockroaches. I find they tend to scatter and disappear when you turn on a light.
The researchers at Case Western Reserve University say that the roaches aren't harmed by the process, and can go on to live their normal cockroachy lives after the power gear is removed. I'm sure Neo will be happy to hear that news. LINK
Think CWRU, via OhGizmo!