One of the posts I made a while back I still get lots of questions about and that is in relation to Bluetooth Car Kit support of Windows Mobile. (http://blogs.msdn.com/jasonlan/archive/2005/11/23/496368.aspx)
The challenge is that differing car kits have implemented differing variants of the Bluetooth standard and profiles making it really confusing as to whether a phone will actually work with your car.
I have a BMW and even BMW's support of Mobile Phone's and Bluetooth is pretty limited http://www.bmw.co.uk/bluetooth/
Very few actually support full capability!
I just discovered this very handy utility which extends Bluetooth Car Kit support for Audi, Parrot, BMW and others.... http://www.jetwaremobile.com/bthfx/support.htm
It's been tested on a whole series of Windows Mobile devices such as:
HTC "Typhoon" SmartPhones Audiovox SMT5600
HTC "Wizard" Pocket PC phones
HTC "Tornado" SmartPhones
HTC "Faraday" SmartPhones
Treo 700w (does not support voice dialing or in-band ringtones)
The best feature I really like is it's ability to choose which contacts to sync. My BMW I-drive has a limit to the number of contacts it will sync and it does it in alphabetical order so I rarely get (m)any of my contacts on the car phonebook :(
This solution allows you to choose by category which contacts to sync :)