Product Review
A glass sensor is useful in case you are worried about an intruder breaking glass to enter a building. Sometimes a security breach can take place where a window is not forced open, but broken instead. In that case a contact sensor may not detect a break in.
The glass sensor is linked directly to your main S02/GSM control panel, so in case the alarm is triggered you will be notified by SMS or a phone call (your own recorded message will play).