Here's a new product that apparently has been used by Israeli military and is now in consumer pre-marketing/pre-order. The responses cover some of the questions and plusses/minuses if you scroll down. Might be worthwhile for a long trip. Would be interested in responses of techies here.

http://mytreo.net/archives/2007/05/fuel-cell-power-pack-sweet-new-treo-accessory.html#more
_________________________
Human Resources Memo: Floggings will continue until morale improves.