My cell phone battery will last for several days with light use. Not many, if any, places in the US you could ride for several days with no AC power outlet available. Of course, if you're playing "green", then solar or hand crank are your options. As there is lots of down time on a bicycle tour, go with hand crank for the upper body exercise.
The most practical and wasteful way to keep gadgets charged in remote areas is with a device like this:
http://www.tekkeon.com/productcart/p...uct=13#details