If you're unsatisfied with the level of geekiness involved with charging your phone, you'll be able to reclaim some degree of street cred with the Epiphany One Puck, a USB charger that uses the heat differential from a hot or cold drink to power a small Stirling engine.
Invented by Scotsman Robert Stirling in 1816, the engine uses the expansion and contraction of a gas within a sealed system to produce power. On the product's Kickstarter page, Epiphany Labs claims it has tweaked the design to the point that not only can it fit inside a portable device, but also pump out enough juice to keep your phone (or other USB gizmo) happy. All you have to do is place a hot drink or cold drink on the correct side (colour-coded red and blue respectively) and watch it go.
The Puck can reportedly supply 1000mA at 5V when operating under peak conditions. When it can't deliver power at this level, it'll store it until it can.
If you're not sure if such a device is possible, one intrepid user decided to punch the numbers into an online calculator that can compute the output of Stirling engines. The result was 5.2W, pretty much spot-on with what Epiphany Labs is advertising.
The Puck has already hit its Kickstarter goal, so barring a catastrophe, it will eventually see the light of day as a commercial product. $US115, plus an additional $US15 for shipping is enough to reserve your very own unit.