NewScientist has a piece about a new battery technology developed recently in Singapore that uses urine to provide electric current. Only a drop or two is needed, but the urine powered battery could actually power your cell phone in a pinch:

The battery is currently suited for use with disposable devices โ€“ it is not yet ready to power laptops or iPods. “But if, for example, we place a small cellular phone or transmitter on a plastic card, the chip will work as a disposable biofluid-activated means of communication in an emergency,”

Until these batteries hit the market we suggest buying a Cellboost.

[via Textually]