Just got one of these today - seems very good. (People were saying my old BT speaker/mic setup sounded like I was down bottom of pit )

Basically, clip to visor - pair it up to phone and it handles all phones calls as per any bluetooth.

And it can broadcast the calls (and music playback on my Desire) via FM transmitter to your car stereo

Only downside so far is that it doesn't remember to use FM when your paired up so you have to press the switch each time you re-link up.

If anyone wants to hear what its like from other end , just PM me your mob and I'll give you a test call