Here is another smartphone charger lets you use fire to recharge your battery. The JikoPower Spark is a thermoelectric generator that turns heat into electricity, allowing you to recharge phones and other small USB gadgets in a few hours (depending on what you are charging).
To get started, fill the reservoir with water to keep the top side cool. The temperature difference between the hot and cold modules changes the electrical output. This could prove useful for camping and emergencies.