£39.84 @ Amazon. New accounts can get 2 for £49.98 and a cheap filler if you are not buying anything else and also use the £15 off!
Extrerior PIR Movement Detector
* 10m PIR detection.
* Up to 30m transmission range.
* 3120W capacity deters thieves by switching on internal lamps, or any plugged in appliance on and off. No wiringrequired