8 Great Hidden Security Sensors to Separate You From DIY Competitors

Nascom Black Hornet Switch — A novel low-profile sensor from the inventors of the Magnasphere alarm contact. The device works off the presence of a ferrous metal object; for example, it senses a screw that’s securing an object and trips the sensor circuit if the screw is removed. It’s a nonpowered closed-loop device that can be connected to any normally open wireless transmitter.