Monster has come out with an iPod interface accessory for your car audio receiver, the iCruze. It will allow users to connect their iPod player to your car systems CD changer or satellite radio port, then display id3 tag info and playlists via the decks display. Alpine has a similar product (KCA-420i) but it is very limited to only newer Alpine decks with Ai-NET bus-link support, making it useless to mass markets.
The Monster iCruze will be more versatile and allow many more vehicles to pump out their iPod beats through their systems. The iCruze will run you $200 and should be available by December 2004.