1. Click on the phone icon on the iPhone
2. Go to the keypad and type in the following command precisely as written: *#307#
3. Once the incoming call screen comes up, click the "answer call" button on the bluetooth, then the answer button on the iPhone
4. Now, hit the home button and get back to the home screen
5. Click on the phone icon again, get back to the keypad and type in 0
6. Answer the phone by clicking on the iPhone's answer button and this time, make sure to click on the "sources" button and click on your bluetooth
7. Now head back to the home screen and start listening to whatever you want - either iPod tunes or any other apps
During this time, you won't be able to use cellular connections or any kind of outside connections to the internet. In order to restore your connections, you'll have to reboot the iPhone once you've heard everything you wanted to.