How about a portable (as in removable) home media server, but for the car. Ideally this would be directed towards families with children on long car rides. It could sync w/ your home library, and allow each child to listen/view the specific media they desire of off their 802.11 device of choosing.

Since it is portable, you remove it from the car during your hotel stay, and again use it in your hotel room to keep the kiddies pacified.