I remembered this article and thought I would post it... http://www.wired.com/wired/archive/9.02/baylis.html?pg=3

I'm not sure how easy it is to find an insert or shoe with these (maybe U.K.?), but it seems like a reasonable option for charging a GPS/Cell/2-way and keeping it charged. The problem comes if you can no longer walk, I suppose, but this:
Voltaic Solar Panel Backpack


or this:
Brunton Solarport 4.4 Watt Foldable Solar Charger with Battery Charger


should fit the bill and probably give you enough for an emergency charge even on semi-overcast days.

I haven't found any shoes that you can buy with that technology, but perhaps someone else can locate an insert for my boots!
_________________________
Experience is a hard teacher because she gives the test first, the lesson afterwards.