Anyone here know about Bluetooth car kits? I am doing some research on new cell phones and am also thinking about buying a new car. Basically, I am thinking about getting a T-Mobile SDA phone with a T-Mobile “Get More” plan. Its not as fancy as a Treo, Motorola Q, or Blackberry but it still has all the features in a nice slim package. It got pretty good reviews from the editors and the users of CNET. Anyways, I want to buy a Bluetooth hands-free car kit. Basically, I would like to be able to receive calls while in my car and without holding the phone up to my ear. I think most Bluetooth car kits use the car’s speakers. My question is if there is a Bluetooth car kit out there that also acts as an MP3 player. I don’t mean that it can play MP3s from a CD. I mean if its possible for me to plug in my phone (which has an MP3 player) into the bluetooth car kit so I can hear the mp3s on my phone through my car kit. I don’t know if an Auxiliary Input jack is whats needed or if the songs can be wirelessly transferred via Bluetooth to the car kit and from there to the car's speakers. Any advice at all would be appreciated.