Watched the YouTube vid. Very cool, man. Duping my comment from YouTube, hoping you check one of these accounts.
"I'm thinking about doing this myself, patching in through a hard-wired FM modulator in my trunk. (Old stock radio.) Had thought about splicing a mic like this, but was worried about echo in voice calls. Have you been on the phone while driving yet? Do people seem to think it's to echoey or that there's too much road noise on their end?
Nice work, btw!"