The Autonet Mobile In-Car Router allows you to turn your vehicle into a mobile WiFi hotspot using the cellular 3G network. Since the WiFi has a little bit of range, you can pull over and use the service while out of the vehicle. Just think of all the times you spend within 100 feet of your car that you wish you had an internet connection. Hardware is expected to go for $399 with a monthly access charge of $49. Expect to hear more about this after they display it at CES 2007.
If it seems a bit expensive for your personal tastes, Ars Technica says that it will be offered in Avis rental cars as well. For the price of a rental car these days, they should just throw this in.
The anticipated draw appears to be that it will maintain connections while traveling down the road. Otherwise, just having cellular 3G service itself would be a much better deal, and more useful as well.