This clever little device called the Simple Start Battery Booster from Black and Decker is selling like hotcakes on Amazon.com (currently for $54.00, 29% off). It's allows you to recharge your car battery from inside your car. It's small enough to fit in your glove box, and can even charge your cell phone, or other devices. Here's the description from Amazon.
Being stranded by the side of the road with a drained car battery can cause anyone to panic, especially if you don't have jumper cables. But you can give your car battery a boost from inside the comfort of your car with Black & Decker's Simple Start Battery Booster Car Starter. The Simple Start puts you back on the road quickly--just plug, charge, and go. No need for jumper cables or waiting for help to arrive. Simply insert the Simple Start's DC adapter into any of the car's 12-volt DC or cigarette lighter outlets and wait several minutes. A boost indicator LED and audible beep lets you know when your battery is charged and ready to start.