I don't think that you got my point:
Oh... trust me... I understood the point
YOU were making. Maybe... I wasn't clear in the point I tried to make.
An
alarm is designed to prevent the owner from being a part of a burglary, and to help notify the police (and insurance) as to exactly when the burglary happened.
The sirens and flashing lights or strobes associated with the
alarm... aids in the notification of the break-in. The use of a simple nightlight will also help a home owner notice that the power is off.... as well as will nonfunctional garage doors (don't expect thief's to RE-connect the power once done ramsacking your home). If your sleeping when the power fails... you may have noticed the "sound" of losing power is enough to wake most people.
But the point I was making was that very few criminals disconnect power or even disable the phone lines. And the ones that do.... AND recognize your home as a valuable target.... CAN NOT be stopped. Burglars have been known to simply cut a hole in the wall of a home with a chain saw... avoiding any alarm/lock problems whatsoever (not to mention just laying in wait for the home-owner to return... and shooting him/her).
Alarms.... NEVER stop burglars... an
alarm is merely one step in deterring a burglary.
It is easy to become too concerned about small details... and as a result miss the larger picture (AKA not seeing the forest for the trees). If you have items at home that attracts a professional... remove them, insure them, expect them to be taken. But for most people... the X10 DIY system is more than enough.