I have the Jabra BT8010 - it's an interesting option...it is a dual earpiece system that allows you to use one or both ear pieces.
The main earpiece is a normal A2DP headset, and there is a second earpiece you can get for cheap that has a small cable that plugs into the main earpiece to provide stereo sound.
So you can use the main earpiece to take calls, listen to music or whatever mono, and if you want stereo, attach the second earpiece. I keep the second earpiece in my workout bag, so I have it when I'm at the gym, and use the main earpiece for calls or mono listening when I'm out and about.
CNET write up: Jabra BT8010 Stereo/Mono Bluetooth Headset Headset reviews - CNET Reviews
The main earpiece can be found for as low as $19 at Newegg...
Sound quality is excellent.