The way security alarm companies typically attempt to secure your windows is by putting a regular open/close magnetic contact on each window to detect when an intruder pries it open. They might also install a glass break sound detector to detect when an intruder smashes the glass. This method is certainly better than nothing but it has a couple inherent flaws. 1) The intrusion isn’t detected until after the perimeter has been breached. 2) Glass break detectors have reliability problems because they are difficult to test and prove they are working correctly, it’s extremely rare for a homeowner to test their glass break detectors regularly. The recent trend has been to use motion detectors instead of open/close contacts and glass break detectors. Motion detectors are generally more reliable and more cost effective but motion detectors don’t detect the intrusion until after the intruder has already entered your home