Since the voltage switches from low to high it can be used in logic circuits.

Other applications are position detectors, keyboard keys, door position sensors for  intruder alarms etc.
 

camshaft sensor 
crankshaft 
sensor ignition 
timing engine speed 
wheel speed (ABS) 
traction control 
wiper systems 
door lock 
central locking 
seat adjustment 
window lifter 
sliding roof 
buckle switch 
brake light switch 
mirror adjustment 
brake assistant 
gear position 
shift-by-wire