If this worked with IR, and so non visible, it might be even more useful.
Great idea though.
But then you would need an IR camera instead of using the phone's camera. An IR camera should be able to find some hidden cameras passively by detecting a heat source.
Pining for the days when phones had IR blasters (e.g. galaxy s6); that would work perfectly for this
Walk around your neighborhood and see who has security cameras.
Security camera through PVS14 https://youtu.be/gEWniEhtE2k