Using mobile as car stereo sort of thing?

I have a G1 phone, soon upgrading to another android platform phone and I am looking for a device if there is one, that will enable me to have the music on here or a telephone call played into the car, without the need for the phone to be on hands-free and playing through the somewhat tin like speakers of the actual phone. Any ideas?|||Your phone will have to be Bluetooth Push capable and the car head unit be able to take BT Push|||bluetooth, USB, Infrared.