It's been awile since I've seen these- and personally, I think that the idea has some merit.
Growing up, we were always told of how fires start because plugs get only partly pulled out, and then get hot. This device is one way to reduce this risk.
The ones I remember were flexible enough that you could bend them out of the way if you wanted to unplug something, but did a decent job of keeping the plug in the socket. The only "downside" was that, with the advent of the three-prong plug, right angle plugs, etc., the things often just didn't fit.
I a perverse way, the use of these things might almost be required by the UL listing- of the alarm system. I wouldn't be surprised if security comes running if this machine gets unplugged- and UL's alarm folks really frown on false alarms.
