Sometimes I suspect that someone might be snooping my private documents. It would be very uncomfortable to place a lock to the drawer, because I open it daily. It's part of my job.
I would need a spy camera that has its field of view 'stenosed', circumscribed only to that drawer I want to keep an eye on.
Thus, if no suspect is close to my drawer, the camera will not activate. The memory could not be filled with irrelevant images.
In my home and my work are almost no ornaments, so I think it would be difficult to see anyone not suspecting of a toy or something similar.