A motion sensor, also called a motion detector or sensor trip, was a type of sensor that could detect movement.
Motion sensors on Christophsis
During the Battle of Christophsis, pressure-sensitive motions sensors were used to guard the shield generator protecting General Whorm Loathsom's advancing droid forces. When triggered by Anakin Skywalker's new Padawan, Ahsoka Tano, the sensors activated concealed LR-57 combat droids which broke through the ground and attacked the two Jedi.
The bounty hunter Robonino used motion sensors under the Rodia swamp to protect an abandoned Rodian station he was using as a hideout. When Jedi Master Kit Fisto and his clone SCUBA troopers approached the station under the surface of the water, the ripples caused by their swimming movements tripped the sensors which activated B1-Series battle droids that Robonino had reprogrammed and triggered powerful blaster cannons located on each side of the sensor.
Kuat City on Kuat's Tekshar Falls Casino had buildup motion sensor to trigger force field to part Tekshar Falls prior visitor was able to enter their establishment.
Industrial Automaton's R2-series astromech droids were fitted with motion sensors.