Why bother with risky battery-changing surgical operations when your own cardiovascular system can provide all the power your heart-shocking pacemaker will ever need? Engineers at Switzerland's University of Bern have been working on tiny turbines; turbines small enough, in fact, to fit inside a human artery. Working like a blood powered hydroelectric generator, a working prototype -- tested in a simulated artery -- has been able to produce 800 microwatts of electricity. That's roughly eighty times the power required to power the average pacemaker; such a device could provide independent, sustainable power to neurostimulators, blood-pressure sensors, and other implanted medical gizmos. Researchers are concerned, however, that a blood turbine's adding agitation of blood flow might lead to clotting, and are continuing to tweak and rework the design to minimize this risk. Similar, but unrelated cardiovascular power designs have attempted to alleviate the concern by doing away with the rotating, fluid powered components, opting to generate electricity by oscillating magnets by utilizing changes in blood pressure -- which sounds awesome, but still falls shy of "blood turbine," in the contest for most Metal medical device.