Have you at a time been alone in a place or someplace with a friend and you get to feel a creep on your skin, like there is a room pinhole camera somewhere spying on you and what you doing? Maybe a hotel room or someplace you never been before and you have a cause to be wary of the environment.
By the way, what are you hiding and why are you doing it? That is none of my business anyway but that which concerns me is how you can rid yourself of that paranoid feeling and be rest assured that there is no prickling eye anywhere, irrespective of what you are there to do (excludes stealing).
It can be a phone or a chip sized camera embedded in the wall clock (You never can tell). Whatever it is, all it takes to detect it is your mobile phone.
Simply turn off the lights, draw the curtains and ensure that the room is dark. Then open your phone camera without turning on the flashlight.
Scan the whole room with your phone. If nothing comes on your phone’s screen, it means there is no hidden camera but if a red dot is found, it means you are right on the radar.
Wishing you all the best in your endeavors.