Whatever happened to the backpack weight shift charger? I read a while back (years?) about a guy that invented a charger that ran off a packs movement as you walked, to build up power. I'm not sure if it used a geared generator, or a spring loaded magnet inside a coil of wire or something. I'm guessing the weight would be worse than carrying one of those 6v lantern batteries, however. I like the new Trent battery packs... If you're charging your phone more than five or six times in a week, why are you even out in the woods?
I've got my old iPod nano (I won at a convention). It weighs maybe an ounce? I bet I could use it a LOT in the woods on a Trent pack