I've been looking at this too, and there seems to be two alternative solutions to OEM CarPlay.
1) You can use mirroring devices like the one mentioned above. I've never used it so maybe someone can correct me if I'm wrong...but I believe that you need to rotate your phone into landscape (cannot be forced for some areas like your home screen.) You potentially need to keep your display on to continue mirroring.
2) There are Carplay adapters that work in the same way as the method above, by tapping into the video input, but then enable carplay/androidauto instead of just mirroring whatever is on your screen. My understanding from their videos is that it works with the steering wheel controls and the OEM idrive controller. E.g.
http://www.unichip-tec.com/bmw_carplay_smartbox.html
I will be ordering the second option in the next few months and hoping it works well. Fingers crossed