I'd love to take a wall, and put in a small hole at eye level. Then place a sign next to the peep hole that reads "Do Not Look In Here."
He should have had the elusive Arduino camera.
In one of Agatha Christie's stories a guy hid himself in a large decorative chest and bored a peephole in it so he could spy on his wife to see if she was unfaithful. The lover killed him by pushing a stiletto through the peephole.So I think I will give your idea a miss....R