I have four of 12-gauge trip alarms that work great! They are lighter and more compact than the perimeter alarm. If the weather is damp enough you can put 12-gauge flair shells in and point them straight up in the air for a great effect.
I dump out the pellets and a bunch of wadding then fill the case up with black powder then put a thin overshot wad on and seal it with candle wax, makes a big flash and is much louder than a case with just the shot removed.
MM