If I understand your goal, there might be a very easy solution: BT Multi-Point hands free adapter. I use the Kinivo BTC455 here: http://www.amazon.com/gp/product/B00JK0G8KC?psc=1&redirect=true&ref_=oh_aui_detailpage_o08_s00 I figure with aptX I don't need a USB DAC. It plugs into the Aux-in on my car. I have it connect to my N7 BT (for media ONLY) AND to my phone BT (for calls ONLY). It works great with Tablettalk. When I get a call in, Tablettalk pauses the music on the N7, shows the caller with the option to answer (phone never leaves pocket). When I answer the call, the Kinivo switches audio feed to the call and its own built-in mic. When I hang up, it switches back over to the N7 with the music resuming. Works about as seamless as it can!