I always take a second battery with me on tour. It's only a small weight disadvantage (less than 50g) to have an extra camera and phone battery. When I have access to power (i.e. when I'm not wild camping) I make sure the phone, camera and MP3 players, plus the spare batteries are fully charged that night. I like the reassurance factor of knowing I have a fully-charged battery in my bag in case it's needed.
I've recently been looking at the iPod Touch and thinking of buying one for an upcoming trip. I notice that an external adaptor/battery pack is available through ebay (from Hong Kong or China) which performs a similar role. Then I found this:
http://cgi.ebay.com.au/Solar-Power-B...item3efea0201a
or
http://cgi.ebay.com.au/Solar-Battery...item563cf6a422
I've had good success with Hong Kong-originated phone/camera/computer accessories bought cheaply through ebay. This device claims to charge an ipod using solar power. It would be nice if it worked. If you search on ebay for "solar ipod battery" it will bring up similar listings. I don't get my iPod Touch until next week but when I do, I'll be definitely taking the risk and buying one of these items. Hopefully if the solar function doesn't work too well, it will still function well as a back-up power source. It seems cheap enough to take the risk anyway.