Here's at least one gadget that won't burden you with yet another charging cord. Tramsystem's i-Blue 757 solar-powered Bluetooth GPS unit (go ahead and take a sec — that's a lot of gadgetry in one device) charges up its built-in lithium-ion battery from the sun. Beyond nixing the power cable, the i-Blue has an efficient power-save mode that will switch off the GPS unit when you don't need it, leaving the Bluetooth active. Then when your laptop or smartphone makes a connection, it'll fire up the GPS chip and give you some coordinates. If you're continuously navigating, a full charge should last you about 30 hours.
It's a nice mix of technologies, but unfortunately the i-Blue appears to be available only in Taiwan right now, so be sure to pick one up for us next time you swing by. Now if only we could make our phones solar-powered, too, we'd really have something here.