Just learned about this, and I’m intrigued. There are a few means of generating some power while on the move and/or away from a power grid. Solar is one, and fire is another (Biolite is one means of doing this, FlameStower is another, and I’ve seen some DIY versions as well.) There are also hand crank generators like the K-Tor Pocket Socket.
Each has their good and bad points. When overcast, the effectiveness of the solar panels is diminished, but they can be used either on the move or in camp. The fire methods seem to require fairly long burn times to generate much power, and they can only be employed when in camp. A hand crank might get annoying/painful for some if cranking for a long time. Some might say that you could carry more than one method, but weight and bulk, and I suppose cost, make that impractical.
This method (http://www.genneo.com) generates power through movement. Which if you’re walking or cycling anyway, is a nice bonus. Carried in a pocket, in the hand, even in a pack works. Shaking it in the hand for a while works. I’m curious whether the movement of a canoe/kayak or the rocking of a hammock would work.
Seems to weigh a bit, which some might consider a negative, but I guess it depends how important power is to you.