I installed a Prodigy recently in my 06. When I mentioned electric brakes the BMW dealer mentioned he had to have another loom installed. when I got the car they had left a brake signal wire under the dash for me to use. I'm not sure where this came from other than it dissappeared over to the LH side of the dash (my car is RH drive).

I ran 3 wires to the rear of the car along the edge of the carpet after lifting the plastic kick plates. +12V, trailer brake and ground. Whatever the wire they gave me provides a 12V signal when the brakes are applied, and surprisingly also turns on the brake lights when I use the hand operated brake on the controller. Not sure what his extra loom was but the dealer said it was introduced to overcome problems with the electric brake controllers upsetting the bulb checking circuitry.

Good luck

Chris,