Parkway Car Stereo

In Japan, Toyota and Nintendo have teamed up so that you can control a Toyota navigation system with a Nintendo DS.
Passengers (presumably not drivers) can input a destination from their DS and view maps and also sightseeing information.
It requires a Kuruma de DS game card (translatation: Use the DS in the Car).  It works over Bluetooth after pairing with a Toyota Smart Navi system.
The Smart Navi system costs the US equivalent of over $2,500 and the Kuruma de DS may be purchased through Toyota for the equivalent of $92. (A DS must be purchased separately).