Here it is not an alarm bell, but a plate. Most places do not have any box outside, except businesses. It is a requirement they must be remotely controlled with someone supervising 24*7. It is not allowed to just ring a bell outside, as it disturbs the neighbours if nobody switches it off.
But yes, some houses have faked plates.
No, they broke nothing. The only thing I had to do was mop the floor from their muddy footprints.
The control unit is mains powered, but the sensors are not. No requirement to power the sensors with mains, fortunately.
I like that idea.