There was a hack a while back that would allow this, but that's not necessary if you use the
Jabra 8040 headset or the
Plantronics 855. Both are A2DP compatible.
I've used them both and although the Jabra is Mono, I can live with that at the times I want to listen to music walking around or riding my bike. Stereo I'll leave to my ear buds. Music cuts out during calls and restarts after the call ends.
The only drawback on the Jabra is no AVRC music controls, but It is much easier to use than the Plantronics unit that was very scratchy after about a month due to the contacts in removing and replacing the stereo piece.