Who didn't like Super Soakers as a kid? You pump it a lot, it builds pressure, then it shoots liquid. In many ways, they were very similar to humans, which is why Lonnie Johnson, its inventor, is looking for ways to use harvest waste heat from humans to power a tiny Johnson system. The full name is the Johnson Thermoelectric Energy System, and it could be up to 60% efficient (standard car engines are only about 30% efficient) at the right temperature.
Not only could it be used to harvest waste heat from humans, it can be used to harvest heat from regular engines or combustion turbines, and has no moving parts at all. The National Science Foundation has granted Mr. Super Soaker funding, which means that we could soon have stuff attached to siphon off our waste heat. Or be connected to the Matrix by robots. Either/or. [Popular Mechanics via Treehugger]