BMW makes a bluetooth kit which can be retrofitted into all US M5s. This allows you to use just about any bluetooth compatible phone in your car.
Do some searches on bluetooth retrofit or take a look at
http://www.bimmernav.com
I have done this, and it really works great. I can see my phone book on my nav display and it also adds voice recognition to your car if you didn't already have that. Best part is that you don't even have to take the phone out of your pocket to use it. (otherwise I always forget it in the car)
good luck.