These types of items are not something that one would usually see in a typical home. They are the half or full dome mirrored security devices that often house cameras. If you go to a department store, you will usually see these types of mirrored housings on the ceiling. The personnel in the store can use the mirrors to see what customers might be doing, including shoplifting. Others are safety mirrors that one would place in key areas where there is a risk of collision between people.