This wireless sensor is most suitable for locations where the position of the sensor and the light/fan/appliance are far apart.
One application is to place the sensor on your table, so that small movements of your hands during typing and moving of the mouse will activate the sensor and keeps the light/fan/appliance switched on.
If you want to deactivate the sensor, simply turn the sensor to face away from you and being unable to detect movement, the sensor will deactivate the light/fan/appliance. Simply, leaving your room will also deactivate after the preset timing.
Some people encountered inconveniences when a sensor was placed on the ceiling because the sensor was unable to detect minor movements of the hand while he was operating a computer and may switch off the lights after a preset time of "no motion".
A table top, battery operated wireless sensor will be able to detect small hand movements.