Does not solve the problem. I already have extras-devel enabled, along with fmcarkit. Still does not solve the problem. Please note the usage:

I enter the car and have not turned FM on. Call comes in. I press answer. I then enable FM transmitter. It does not route through the FM. One can hear the FM beeping, but the sound is still through the speaker on the phone

Seems extremely silly that the above doesnt work. It seems common sense. Just like being able to turn on speakerphone at will during the call.

What everybody is suggesting is the opposite. It doesn't make sense to turn the FM car kit on every time one enters the car, and then off again when out of the car, in the 1/10 chance you might get an incoming call during it. In the event you forget to switch off the FM, and a call comes in, you won't hear the other person when you pick up. I don't use the media player on the phone, I already have an ipod hooked up to the headunit by headphone jack

I don't know if its possible, I'm just clarifying what it is that I'm asking