We have the Pioneer radio (2018) with integrated back-up camera, also the nav. system. The radio can pair with a cellphone via bluetooth for calls. The microphone for that is at the top of the windshield on the driver's side. It is not connected to the back-up camera as far as I know however. I have not seen any kind of mic at the camera either. I would think a voice picked up by the camera would be heard by the driver anyway.
You could pair your phone with the radio, call your spotter's phone and talk hands-free that way. Or use the speakerphone on your cell with your spotter.
Small headset communicators like walkie-talkies also work to allow normal conversation between the driver and spotter.
If there is a mic built-in, I too would like to know about it!
Steve