In 2010 your mobile phone may be powered by water. During the 2007 Korea Electronics Show. Samsung Electro-Mechanics announced that it has developed a micro-fuel cell and hydrogen generator that runs on H₂O.
And it even showed a working prototype of the new "Micro Fuel Cell" which works with the Korean version of the Samsung SGH-i600 (I wouldn't mind to test it as well). According to Samsung, the micro-fuel cell can generate up to three watts of electricity which is enough to be used in mobile devices. The new fuel cell could power a handset for 10 hours (talk time, standby time?), twice as long as rechargeable batteries.

"When the handset is turned on, metal and water in the phone react to produce hydrogen gas," explained Oh Yong-soo, vice president of Samsung Electro-Mechanics' research center. "The gas is then supplied to the fuel cell where it reacts with oxygen in the air to generate power. Other fuel cells need methanol to produce hydrogen, while Samsung's needs only water."
"If the user uses the phone for four hours a day on average, they would have to change the hydrogen cartridge about every five days," Oh said. "Later handsets will be developed that don't need the hydrogen cartridges to be changed, and would only need to be filled with water."

According to Oh, the water-powered handsets are expected to hit the market by 2010.

Cheers ~ Arne