A nice thing about using an inverter (especially a reasonably hefty one, like 250 watts) is that you can plug a power strip into it and run a bunch of things off of it at once - a laptop, say, plus a cell-phone charger, plus an EnToURagE charger. There's not enough power to run an electric lawn mower, I don't think. These things won't fit in the glove compartment, but they will fit under the seat.

Another nice thing is that you've got a regulated output, so you won't fry your device.