Theres all sorts of things made to look like inanimate onjects but which are actually cameras... pens,car key remotes, caps, sunglasses, even a motion detector or fire alarm in a room.

The secret is none of those small covert cameras have very good IR capability so if you suspect something is up, make the room as dark as possible it wont pick up decent images in the low light. Those that are hardwired into the house electrical system can be hidden however as per the above, behind a 2 way mirror,inside a vase or some other object of decor in the room, even the spine of a book on a book shelf which of course isnt a real book but a housing for a camera