Another development in portable power has just been announced Rocket of Korea: A new, paper battery. This  very thin, flexible battery could be used in credit cards or other very small (and presumably low-power) applications. The battery has 1.5 volt (nominal) output, but only provides 1.5 mAh (as compared to 750 mAh on a AAA NiMH rechargeable I have at hand here).

Even better, the battery is reported to be eco-friendly by being incapable of "polluting or releasing toxic ooze or combusting under pressure."

I'm sure this will be scaled and refined as development continues. Combine this with some flexible display e-paper, and you could have a very book like device that allowed for a changing, computer-like display.

Via Wired Gear Factor