Why get things so over-complicated and over-priced with the bluetooth retrofit kit (you're looking at over $700 worth of hardware alone) when a simple solution exist for about $50 from most online stores => http://direct.motorola.com/ens/carkits/learn-T305.html. I just got one for my sister and must say that it performed pretty well for a tiny device. If you want to blast your conversation (or music) through your car speakers instead of the built-in speaker, then wait for the T505 => http://direct.motorola.com/ENS/T505/T505_Home.asp

BMW electronics are already so finicky that you're only asking for trouble with any retrofit.