What do you think would be involved in getting the FM transmitter to be a selectable "audio out/DSP" device for phone call audio? That would basically put the phone in something similar to 'speakerphone' mode, with the onboard mic still picking up the audio to be transmitted.

I think just a modification to /etc/pulse/xpolicy.conf to add an audio path there, and some sort of script/UI change to give a button on the call screen.. right?

The fm transmiter is listed as device:
crw-rw---- 1 root video 81, 0 Dec 31 1969 radio0

Let's get some ideas going. I have a few really good developers at my disposal if I ask nicely...