I though that I had found a solution to allow me to integrate my cell phone with a car head unit. The Panasonic CY-BT100U is a handsfree kit for Panasonic head units. When a call is received, it automatically mutes the audio and shows the CallerID on the display of the head unit. Then you press the button on the dash to answer the phone call.
One thing that I don't like about it is that you can not make calls with the car kit. Also you can't make calls with the phone when it is paired with the car kit.