There are really only two obvious solutions for backpackers to keep electronics charged out in the boonies.
There’s the more conventional route of using a solar-powered battery, like the Joos Orange, or Solio’s line of chargers. Or there’s the less common alternative of using one of an increasing number of stoves that can charge gadgets while heating dinner or water for coffee.
The upcoming newest member of the latter group, the PowerPot X (that “X” is a 10, btw), can even charge an iPad.