what determines whether BT button starts up voice dial?
 

I recently had a Pioneer stereo in my car and it was extremely convenient: it paired as soon as the car was turned on, and hitting the phone button on the stereo immediately launched voice command through the radio's sound system, so that I could dial by voice and never have to take the phone out of my pocket, unlock it, etc. My car was totaled in a crash and in the new vehicle there's a separate BT system which doesn't seem to do any of this - it pairs and calls come through it, but it won't activate voice dial. So I'm thinking of replacing it, but I need to know: what feature am I looking for that enables the radio to connect to the phone and launch voice command without me having to touch the phone at all? What determines this?

Thanks,

Mike