I'm considering buying a Garmin Nuvi GPS unit with bluetooth. I have the BMW Assist with Bluetooth option on my car, which means that when my bluetooth phone rings, the system automatically turns down the volume of my stereo and rings the phone thru my stereo speakers.

Does anyone know if bluetooth GPS units will work the same way? Will the system fade out my stereo and play the GPS audible instructions thru the stereo speakers in place of the stereo music??

thanks!