I do think some at least of the new generation cameras will come with a external MIC connector, but i am not quite sure if this will just be for dashcams thats the camera on a wire solution like the SGZC12RC.
Perhaps
@jokiin from Street Guardian can tell a little about what they have coming in this regard.
May be a little problematic as many dashcams is of the popular wedge shape that go fine on a car windscreen, but i am not sure how suited that would be for a ****pit window / windscreen.
Off course you could make some form of bracket / adapter that would widen the places in your plane where you can mount it, cuz i assume just put on the windscreen and filming strait forward thru the propeller would get a bit boring.
I do know the up and coming dual channel cameras from Street Guardian will be with a external microphone thats provided with the kit, at least for the planned 2 cameras on a wire version later next year.
And that would be pretty sweet in a plane i think, 1 camera to film where you are flying and then you could use the rear camera on a wire inside the ****pit for all kind of angles, or maybe outside on the wing like that guy also do with the action cameras.
I think the 2 cameras on a wire would be perfect as its pretty darn small camera units, so you could stick those just about anywhere you would like inside the ****pit, and maybe outside if you have a secure way to do that zip tying the wire to something.
I am pretty sure you will be able to wire the audio out of your intercom into those up and coming Street Guardian cameras.