A much simpler (and cheaper) solution is one of these:

http://www.gomadic.com/battery-backup-cat.html

It takes AA's and you just get the correct tip for your regular phone and works with virtually any device. I got one of these for a week long bicycle trip I did last summer and used it to recharge my cell phone and GPS every night in the tent. It would recharge my phone in an hour or so. Or you can operate the phone while it's plugged it. I keep it handy at home with plenty of spare batteries for emergencies. I even carry it on long plane flights to recharge my music player if it gets low mid-flight. I only payed about $20 for it and it was well worth it.