As a new owner I have researched several different options of bluetooth integration to my iPhone for the E39 M5. I simply found that I would rather spend more money on other things, so I decided to come up with my own.
Some things were a must have on my quest (in order of importance):
1. Reasonable pricing - found a new Parrot Bluetooth Minikit Speakerphone for only $49.99 that included shipping
2. It must power on when I start the car - I hardwired it so it is always on
only when the car is, so I don't have to worry about the battery
3. It must be loud enough - Parrot knows this is a must and it is loud and clear
4. It must integrate nicely with the car
and not have a chance to fall or slide around during "spirited" driving. The black and silver color scheme match the interior and exterior colors of my M5.
5. Synchronizes phone book with iPhone - Parrot built in functionality
6. Hands Free Operation - I can dial by voice commands
I installed it the same way I hardwired my Passport 8500 X50 Radar. It is all connected to the HomeLink transmitter ACC power wire. So when I turn the car on the Passport and the Parrot Bluetooth come on and when I turn it off, all of those devices turn off (the Parrot stays on for a while until the internal battery dies on the Parrot).
For $49.99 this is how it turned out.