Sorry... it is the box that installs in the center console to hard wire a cell phone. In the days before bluetooth, BMW used to sell a special phone (the CPT9000) to interface with the car by plugging into a slot in the arm rest. Well, that box is still sold.

What happens is you connect this box to to the car's wiring (which is already present inside the arm rest) so that your phone can take advantage of the built-in cell antenna and also get charged while in the cradle. In addition, it hides the phone under the arm rest.

http://realoem.com/bmw/showparts.do?...08&hg=84&fg=20