I bought the cameras when I put my house on the market after I found items moved and was not sure if a couple of items went missing or I had a brain drain and lost them. Since then the cameras have given not only peace of mind but a view into what the prospective buyers were thinking and how the agent worked (or not) to highlight the house and property.
I have cameras covering all areas and in a 2900 sq. foot house only need 5. This lets me see what people think about all areas of the house and has offered ideas on what I needed to change to secure a buyer.
It also lets me give feedback to my agent about agents who I do not want back.
One thing I have been searching the forum for is hooking the camera into a battery pack so I can make the cameras more discreet since some folks have given feedback they left because they did not like the cameras watching them.