I have seen 1 or 2 'powerbricks' around. They are basically a big battery pack that allow you to charge up or run another device, like an iPod, Pocket PC, digital camera or whatever in situations where you normally don't have easy access to 110/240v - such as a Camel Caravan in the Sahara or on a long-haul aircraft flight. The problem with these commercially available things is they are freakishly expensive.
Here is a nice DIY version to try:
