Ok this is something I have wished the iPhone did for along time. I have a car that has enables me to pair my phone and car via Bluetooth. However I could not stream music or other app related audio via Bluetooth. I could only make phone calls. Now with 2nd Generation Bluetooth or A2DP you can.
What do you need to do to achieve this. Well you need your car to be A2DP compliant and very few are except for some of the very latest models. So what to do. Easy. Make your car A2DP compliant with a A2DP receiver that funnels audio into your AUX port which is a feature that most cars from the last few years have.
I use a device called LiquidAUX™ Bluetooth® Car Kit. Check out the link to the item on Amazon.com below.
I use it in my car and I have to say it works like a dream.
The beauty of this sucker is that it plugs into your power port in the vehicle and has a short audio lead which you plug into your AUX port. In my car they are right next to each other in the center console so it works like a charm. Simply plug it in, pair it with your iPhone as per the instructions and away you go. Simply switch your car audio system to AUX and hey presto you will hear your Iphone audio thru your car speakers. Sweet. It does not interfere at all with your phone bluetooth pairing. They operate completely independently from one another. You can take phone calls and when you are finished the last app you had open will launch again and take off from where you left off. Nice job Apple.
Happy A2DP Audio Streaming.
UPDATE: Of course you can just connect your iPhone or BB directly to your AUX port with a standard device compliant audio cable. Works just as well. Not as pretty but it does the job.