Phat: I was thinking about this one: Integral Designs Siltarp 2. Backcountry.com is out of stock, but Amazon has it for $135 and change, plus shipping. This is the sort of thing I'd take if hanging were not an option, or if setting up a base camp, or with the family trip I outlined above. The price is way beyond what I thought I wanted to spend, but from what I can see it may be worth it. I'll be looking around some more before I jump.

Lori: That sounds like just what I want, then. My BlackBerry uses a USB for charging and connecting to the computer, and if the ports are the same size then the car charger I have will work. If not, no biggie. I have used both Energizer Lithiums and the rechargeables in my camera, which is a power hog, and I like the lithiums better. They last much longer than both alkaline and rechargeables. Since both camera and GPS use the same size, taking spares is less of a hassle.

Thanks for your help so far!