You can use a solar panel-equipped backup battery to charge your mobile devices. If you want a more innovative option, the following Epiphany onE Puck portable charger should be able to catch your eyes.
Epiphany onE Puck is an innovative, eco-friendly portable charger. As we can see from the images, the portable charger looks like a USB heater, of course, don’t be fooled by its appearance, in fact, you still need to put a cup of heated or chilled drink on the portable charger, but using a built-in stirling engine the coaster-like USB charger can utilize heat disparities such as a hot or cold drink to provide enough power and charge your cell phone. All you need is only a cup of heat or cold drink on the charger. Moreover, the portable charger supports all iPhones, iPods and Android phones as well any device with 1000mAh or less battery.
At present the team of Epiphany onE Puck is raising fund at Kickstarter. Pledging $$115 will let you own the innovative USB charger. If you’re interested, jump to Kickstarter official site for more details.