ive got a sony bluetooth headunit cost about 100 uk pounds from halfords

it is handy to have the bluetooth avalible

as soon as i get in my car it auto connects to the headunit

it then gives me my whole music collection to play via car stereo controls and when a call comes in it auto switches to phone mode and i press the volume key in and it awnswers the call for me making the call come out of thew car speakers

the bluetooth stack on the n900 isnt as stable as say my n96 n97 5800 etc etc as sometimes it gets stuck in phone mode and the quality isnt great this has only happend a couple of times but it never happend with the other phones

if you have a tv in on your headunit you could have your n900 connected to that and play angry bird on your car dvd player screen :-)