Quidzel offered integrated bluetooth modules in the past. However, we can deliver better value for our customers by focusing on the simplest aux input for older BMWs. We found it was hard to beat a simple solution that would plug into our aux input. Personally I had a good experience with the MPOW Bluetooth Receiver for under $20, sold by Amazon:
I found the sound and overall quality to be decent for the price, the battery life is excellent, and it paired well with my iPhone 6. If you need to charge your phone or a bluetooth dongle, you may run into noise created by an audio ground loop. An inline audio transformer like this should kill that buzz: