I was messing around with the BMW iBus a while back and found a few repos with complete garbage code that was super useful for getting an idea of what the protocol looked like. Of course I didn't end up sharing mine, but ended up selling that car before getting beyond "wow it works!" :(
I had a 2003 530i, which didn't have aux in, nor bluetooth.
My use of the iBus was to emulate the CD changer in the trunk (basically just a heartbeat every 7s or so) which allowed me to use that line-in. I also picked up button presses on the bus in order to respond and control audio playback. Tied it all together by using a raspberry pi as a bluetooth sink and command hub between connected phone and the iBus.
To be fair, that car saw quite a few instances of the other type of "working on the car" too. I have 58 entries in my work log from two years of ownership...
