Motion sensors come in a wide variety. You can get add on sensors for your existing alarm, as well as stand alone units for windows, doors and driveways.

MOTION SENSOR DETECTOR HOME SECURITY SIREN ALARM SYSTEM
US $9.75

Motion Sensor Security Alarm Siren IR Motion Detector
US $10.44

Remote Detector Security Motion Sensor Alarm Infrared
US $5.99

MOTION SENSOR DETECTOR SECURITY ALARMS+REMOTE CONTROLS
US $59.95

MOTION SENSOR SENSING DETECTOR ALARM+REMOTE CONTROL LOT
US $43.95

PIR MOTION SENSOR DETECTING ALARM+REMOTE CONTROLS LOTS
US $28.95

LOUD MOTION SENSOR DETECTOR ALARM WITH 2 REMOTE CONTROL
US $25.95

2 New Wireless Sensor Motion Detector Security Alarm
US $4.99

IR Wireless Motion Sensor Alarm Detector Night Light US
US $6.00

MOTION SENSOR DETECTOR HOME SECURITY DOOR ALARM SYSTEM
US $9.75

Motion Sensor Detector Front Door Entry LED Light NEW!!
US $18.00

MOTION DETECTOR ALARM w/ Keypad! Security SENSOR +STICK
US $13.70

Wireless Driveway Security Alarm Motion Detector Sensor
US $24.00

Solar 15 LED Security Light IR Motion Detector Sensor
US $24.99

Solar 15 LED Security Light IR Motion Detector Sensor
US $24.99