Say you have a puzzle where the solution is for the player shout into the mic to startle an npc, or where the player has to stay quiet as they're sneaking by something. It doesn't have to be able to tell what the player is saying or anything crazy like that, just detect whether a mic is picking up sound. Is there anything like that?
AGS doesn't natively have any way to detect microphone input. You would need a plugin.
I once wrote a AGS plugin that recorded input from a mic into the file (using SDL2), that in turn could be loaded an played in the game; so that's definitely doable.