Several years ago I came across "Fuel Cell Technology".
Hitachi was one of the brands that put some money into this research as well as people like Toshiba.
The idea is to generate electricity by just adding water to a "fuel cell".
This is the first generic (IE not specifically designed to work with a particular product) charger that I know of.
Not ready for retail but should be available soon.
http://www.powertrekk.com/product/as well as being able to charge small devices (cameras/phones/MP3 players) directly via a USB connection , I suspect that it could be hooked up with one of the new AA/AAA chargers that can be charged via USB , so it looks rather promising to me.
Obviously not that use full for a short hike...
A funny comment I read about this was " what is wrong with solar panels ? we always have the sun, don't we ?"
(the guy was serious...)
Franco