I'm interested in trying to buy a raspberry pi and create a small bluetooth / airplay type module that I can plug into my car somehow and get wireless audio streaming.
I don't necessarily care about getting steering wheel controls, I really only care about audio at this point, plus I know there are some solutions that I can purchase other parts with to get that done, those are a little too expensive for me right now an I just want to get something a little more simple to get me started with raspberry pi.
My first thought is to either tap the CD changer cable somehow to pipe the audio into the system or take the disc changer out all together and plug straight into the existing port.
I have been looking for a connector that would let me do the latter but I have not found anything so far so I'm thinking the first option may be the way to go here but I'm not really finding much on this subject either.
Are there any tutorials or write ups that talk about patching into an existing CD changer or something similar with raspberry pi or something of that sort that I can be pointed to. I'm sure if I see the basic workings of getting the audio in it's just a matter of my imagination going to town on getting my phone to connect to the raspberry pi (which seems easy enough given all the numerous tuts I have found on that subject).
As noted in the comments, most modern car systems use a digital protocol to control the CD changer. Even if there are analog audio leads, the head unit won't recognize it without digital signals from the CD unit.
In any case, the solution will be specific to your car and possibly the specific head unit. If you search (Google, etc.) for your car's model and terms like "add aux input", you may find more detailed info. You may get lucky and be able to use a fairly inexpensive adaptor.