I think realisticaly there is a point for a special traveler's cellphone - take one with you when going hiking and know that you will be able to call help no matter what happens. That sort of thing.
http://www.voltaicsystems.com/bag_generator.shtml
15w solar laptop briefcase.
A lot of things you make must be cheap, must have own power source & must be useful enough to (a) justify spending money in a place without much (b) worth the hassle of putting panels on your roof or whatever.
What seems relatively sensible is a solar powered desktop to start with.
I'm not saying these things aren't a good idea, I'm just saying most people live in highly urbanized areas where leaving stuff like this in the sun will get them stolen. If you want to take a laptop with you on a fishing trip or into cottage country, then this is ideal.