OK. So we have solar chargers, regular wall chargers, and of course packing in extra batteries as kind of the typical way people recharge their devices.
Then there are also thermocoupler devices like the power pot.
But what else… I had some other ideas.
1. Steam!
Here is an example.
http://www.instructables.com/id/Steam-powered-USB-Charger/
It's kind of a silly idea but if you could use your pot and a wood stove (gas wouldn't make a ton of sense) you could build a charger. WEIGHT is the issue here. I haven't done much research but it would be interesting if you could get a basic steam powered charger working for USB chargins.
2. Hand crank…
This one:
http://www.amazon.com/Innovative-Digital-Hand-Crank-Emergency-Charger/dp/B0089QB2KY
is 32 bucks and 90 grams. My second battery is 70 grams and I suspect you could get a lighter one. Apparently 6 minutes of cranking gives you 2 minutes of talk time. So this seems somewhat practical.
I was also thinking that you could use the water from a stream to power this. Maybe use gravity to turn the crank.

