Here's a brain bender: Korean scientists have developed a way to turn sound into energy. The idea is that such a system could be installed in a mobile phone and the phone could charge itself based on you talking into it, holding it up to traffic, or even playing music. I guess if your battery is really low, you could just sit there and scream your lungs out, which would be bad for society but potentially hilarious. Cuts both ways. From the Telegraph: The technology uses tiny strands of zinc oxide sandwiched between two electrodes. A sound absorbing pad on top vibrates when sound waves hit it, causing the tiny zinc oxide wires to compress and release. This movement generates an electrical current that can then be used to charge a battery.
Early tests have shown that it works but still doesn't produce much power. Scientists are working on modifying it and making improvements.