Most every home in America has sensors of some sort. Many homes have exterior motion sensors that activate floodlights for some measure of security. From there we move up a nearly boundless slope of sophistication involving networked, intelligent, and active sensors for intrusion, burglary, and fire detection systems. Even linear sensors, such as thermostats, are calibrated at the factory or by integrators to open and close electrical contacts at certain temperatures.
Applications vary, but sensors typically act as triggers for programmed events.
A thermostat shuts off an air conditioner. A motion sensor turns on a floodlight. As an example, Welnicki demonstrates a sample application using a variety of sensors networked with Elk's Magic Module programmable controller. A homeowner arrives at his usual time through the garage. The motion sensor there registers his presence.