Dogs, large fences, lights are a excellent one esp. motion lights.
I would think that any thing that has a lot of sharp points would work.Would cactii work as far as lining the perimeter entry points or do they grow too slow? Are there any that grow really fast?
We use a charley bar to secure our apartment and hotel rooms from intruders. They seem to work very well.What does everyone use as far as devices to prevent burglary besides firearms and alarm systems?