I tried the Denon Exercise Freak bluetooth headphones - I returned them due to connection problems. They'd find my iPhone just fine, but the music would crackle and break up while I was riding. There was a clear line of sight between the phone and the earphones as I ride with the phone on a holder mounted to my stem. The head phones had a supposed range of 30 feet, but the 2.5 feet between my phone and ear thwarted them. They were about $150 new, so I expected them to be perform better than they did.

That was in February - not sure how blue tooth headphones have devloped / improved since then.