I just wanted to share my experience with my BlueAnt Q2 Bluetooth headset. I know most people carry their cell phones when they ride as do I. I have been very impressed with this headset.
I have used a number of different head sets from wired to a couple of different Bluetooth headsets. By far, the Q2 has been the best of them all. Its noise/wind cancelling technology is superb. I can ride at 18 mph and carry on a conversation. I was even mowing my lawn with a gas mower and was able to easily carry on a conversation using this headset.
Not only are the phone functions excellent, it also streams all of your phone audio to it so you can listen to music, GPS navigation, lap times from your cardio app., or anything else as you are riding. Most Bluetooth headsets will only do phone audio.
It also has a handy voice interface. So if I get lost during a group ride, I can just tell it to call the ride leader. You will have to program the group leader's phone number into your phone first of course. It isn't psychic.