One of the cool things is this iDrink bikini with solar cells.
The photovoltaic film panels on the bikini can supply 6.5 volts @ 1.5 Amps which is enough to power an iPod. The bikini has a retractable USB connector which can also be used to connect to a peltier to keep your beverage cool.
It's a cool gimmick but not really useful as it doesn't really like water. A bag with photovoltaic cells is a bit more use full IMO (this already exists by the way).