While it would be cool to power an iPad with your body heat, we probably don't have to worry about being enslaved to power a giant computer network like in the "Matrix" movies. Humans are a potential source of electricity, but a fairly limited one. An adult male, for example, theoretically might be able to generate 100 to 120 watts of energy. That's not going to light up the Empire State Building, but it might be enough to power some personal electronics devices -- a laptop requires about 45 watts, and a cell phone only needs about 1 watt to operate [source: Ozcanli].
That said, researchers still have a ways to go before we're able to leverage a significant portion of our bodies' potential to generate electricity. While the idea of power felt has promise, the initial demonstration version only has the ability to generate about 140 nanowatts of juice [source: Zhang]. The villainous Agent Smith from the "Matrix" movies would be disappointed, since that's only about a billionth of a watt. Other available conductive materials for converting body heat to energy don't do much better. By one estimate, such devices are able to harvest about 0.4 percent of the body's heat energy and convert it to electricity. That means that if you covered your entire body with thermoelectric generators, you'd only produce 0.5 watts of electricity [source: Ozcanli].
Still, though, we'll probably improve on that performance over time, and also simultaneously develop electronic devices that are far more efficient at using energy than the gadgets of today. Researchers already are working, for example, to develop super energy-efficient medical sensors that could run off a patient's body heat. But the real upside of power felt may come from using it to capture heat energy wasted by our machines. Recent research at the Massachusetts Institute of Technology, for example, indicates that by tapping into wasted heat from laptops and cell phones, we might be able to do the equivalent of doubling their battery life. Lining automobile engines and the inside walls and pipes of power plants with power felt might yield a vast supply of electricity that we never even knew we had [source: Chandler].