Gadgets like the iPhone and iPod include their own USB-based charging cables. But most other mobile gadgets can also be powered via USB. This list includes nearly all cell phones and Bluetooth headsets. (The big exceptions are laptops and portable DVD players, because their power requirements exceed USB's 5-volt load.) So the first thing you'll want to do--after verifying that the device in question is chargeable via USB--is to get a matching USB charge cable.