Way overpriced
For anyone who can read and follow basic instructions one of the many wireless alarm systems on eBay is much better value.
(For example "HOMSECUR Pet Friendly Wireless GSM Autodial Burglar Alarm System+720P IP Camera" at £197.49 has 4 PIR sensors, 9 window/door sensors, smoke sensor, video camera, inside and outside sirens and battery backup.)