This is a cracking deal, I bough one when they went down to £82.99 (+ delivery).
Will post the link to MSE discussion from last year on this later.
Easy to install
Supports up to 28 sensors(PIR)
Alerts designated contacts via phone, email, SMS
Monitor the status of your phone, via Internet
Keyfob- now includes 1 Unit
Magnetic Detector- 1 unit
Movement Dectectors- includes 2 units
3 Months FREE monitoring service