I do not have Bluetooth but do have a hands free set up through my Alpine head unit (& Sat Nav) in my Insight - phone holder (& charger) to the left of the steering wheel next to climate control sensor (right hand side on US) and the microphone clips nicely to the top of the plastic sleeve on the windscreen pillar.
Talking of Bluetooth, I read an article the other day that aimed to dispel the urban myth that the Prius can be 'hacked' via Bluetooth. A team spent hours trying to do this and the best they managed to do was freeze the dashboard display.
We have a 04 Prius with Bluetooth and it is nice. I have a headset with the phone which works but considered putting one of those add on's that tap into the stereo for automuting and putting the caller on the speakers. Have fun, RIck