Over here in good old europe, the so called CarPC or Carputer is becoming more and more famous. For about 1500$ you can have everything you want like GPS, DVD, Games, Internet, WiFi, MP3 and so on. Maybe you like to check out these pages : www.car-pc.info or www.cartft.com. Sorry for both pages beeing in German, but maybe you can use babelfish.
Cheers from the "old world"