On the ground: Fuel cells
Fuel cells are batteries using liquid chemicals that can power or recharge a device, by using external sources such as hydrogen and oxygen. For years now various companies have promised to bring fuel cells to cell phones and other mobile devices, to solve the old problem of shorter battery life in modern devices.
It seems that this technological breakthrough will hit the selves this year after all, according to Medis Technology at CES. They will sell a $19.99 Power Pak which will be able to recharge batteries, providing an extra 60 hours of battery life to an iPod or 30 hours for a cell phone.
The main issue with fuel cells is the complexity of making small ones. Last year Nokia stoped development on some fuel cell projects because of complexity and logistics problems. We're not yet at a point where we'll see hydrogen powered cell phones, but it may not be too far off.