I read a review here on SharedReviews awhile back and it was about one of these home security alarms. It was on a window for to prevent buglary. However my reasoning for purchasing these where for a totally different reason.
I purchased this because on night i heard my side door opening in the middle of the night. I jumped out of bed so fast as i just knew what was happening. My one child sleep walks. I woke to finding my daughter in between the house door and the screen door.
Well that did it for me. I found this alarm system at the Dollar Store to my surprise. It also came with batterries. And still work to this day. We ended up getting one for each door and window in the house.
They are very easy to install. All you do is take the paper of the sticky pad and paste it on. You would think these wouldn't work. But they do. And well too I might add. For the windows all we did was turn the switch on. If the window opens the the alarm sounds. As for the doors we set them to on at night only as the alarm will keep going off everytime you open the door.
I just feel so safe knowing that if our daughter tries to sleep walk out of our house again. I am sure to hear the alarm if I don't her her walking around. I also feel safer at night knowing if anyone tried to break in we are sure to here it. The alarms are load enough to draw attention to anyone outside. However once the window or door closes the alarm goes off. So this alarm works for us for what we need it for.
If wanting an alarm for burglaries when your not home. I would suggest a more valueable system.