All kinds of Bluetooth phones work with the BMW Bluetooth systems. If I were you, I would turn the question around... find a BT phone that you like, and then query this forum and the
www.bimmerboard.com/forums/bluetooth forum for examples of people who have successfully used that phone with BMW BT.
Sony Ericsson phones probably work the best, since they seem to have the purest implementation of the BT standard. My Motorola RAZR phone is very good, but some carriers lower the BT volume on the phones in their branding. All of the Blackberry BT phones work pretty well too. (I currently use a BB Pearl, and it is fantastic.) I have also seen folks post successes with just about every other phone brand, like Siemens, Nokia, T-Mobile SDA, LG, Palm, Samsung, etc.