first off http://www.navigadget.com/ is a great website for navigatation information
and i jsut found this on that website
turn any entertainment system into GPS navigation system
With Dotelís (dream of telecommunications) Navi Box (DOTN120) you can turn any in-car AV system into an GPS navigation system. DOTN120ís small form factor allows you to easily install the device anywhere in your vehicle while giving you the freedom to move it from one car to another. Before you install this device you need to have an already existing LCD screen that can accept A/V input.
It supports diverse interfaces for A/V device including A/V out, Stereo audio out, even RGB out. And it can be connected to Sandard Car-TV or Indash-DVD Player, and all kinds of A/V system which has screen. Easy and simple user interface with remote controller enable you to use the unit more conviniently. You can even enjoy mp3 music while driving.