I have an iPhone, and while in my car, I can connect to the radio through my AUX jack and use the phone that way. The iPhone microphone picks up just fine and I hear the person through the car speakers. While I don't think Apple intended for it to be used this way, it works just fine.
My mom has the Samsung Moment, and when we tried that in her car, I couldn't hear her at all. Does Android disable the microphone when an aux cable is plugged into the headphone jack? If so, is there any way around it? Has anyone had success with using an Android phone in a vehicle radio like this?