A well-trained, intelligent dog is probably my favourite security precaution. A member of the family that eats intruders - what more could you ask for?
I've got a Boerbul. It's a local breed originally bred to defend livestock from lions.
Lovely beasts, ferocious defenders of the homestead, and great family animals.
I once ran out into the backyard to investigate a scuffle in the middle of the night to find her with a bloodied and torn shred of pants-leg hanging from her mouth.
The would-be burglar vaulted over my wall like an Olympian, and a neighbour from two houses down found him limping through his yard after I'd alerted the street.
(this isn't mine, but you get the idea)