Solar power is slick, and easily takes the Kemix Bluetooth GPS Receiver from generic Taiwanese knock-off to noteworthy. There’s a battery inside, of course, but the solar panel, in bright sunlight, can extend the regular operating time of 20 hours to around 30. Considering how many people use GPS while walking out of doors, it’s even potentially useful.
Bluetooth Solar Powered GPS Receiver [Blueserker revia UberGizmo revia Pocket-Center.de]