We carry around far too many portable devices with us these days, so it only makes sense to get a single device to do as much as it possibly can, right? Why not get your smartphone to pull double duty as a GPS navigator by simply adding on the tiny Holux GPSlim 240? This SiRF Star III receiver can wirelessly sync up with your smartphone, PDA, or notebook computer via Bluetooth, and it will keep itself running for a solid eight hours from its integrated lithium-ion battery. Alternatively, you can opt for a few cables: USB for connection, car charger for juice. The Holux GPSlim 240 is pretty cheap too at just $99.