Everything these days seems to recharge via USB plug, like cell phones and Bluetooths (or are they technically 'Blueteeth' in the plural?).
Convenient when you don't need to carry a dozen chargers, but inconvenient when you're nowhere near a computer with USB plugs.
We love this ZipKord Dual USB Car Charger because it lets us top off the charge on our gadgets in the car, and we can still use a cigarette-lighter plug at the same time.
Scott wouldn't go on a bus trip without it!