Can't you use infrared cameras like the FlirOne and just search for things that are weirdly hot? Most cameras should generate a lot more heat than its surroundings.
One would need to look up the type of battery and how long the camera runs on that.
I think it's a good idea, but especially in cases of non-continuous monitoring (e.g. 1 FPS or way less) with modern low power electronics this could become quite difficult.
Better yet, would be a law passed that outlaws photographing people without their consent, at least while at work. I heard France has strict laws that protect privacy.
I've never liked my picture taken without my consent.
Assuming your work takes you anywhere outside, or in a vehicle, or in any public area, you have no reasonable expectation of privacy.
You can't reasonably expect someone photographing a public place to announce to everyone they're about to take a photograph, or get a waiver from everyone, or blur the faces of everyone who they can't get to sign.
