Always felt a bit hard done by that insurance companies never gave me discount for my four legged alarm, my German Sheperd ! Best deterrent of all imho.
My brothers state of the art alarm system proved useless when the burglers pulled the box of the wall, dumped it in a bucket of water, broke in to his house and stole 7 grands worth of jewellery and were gone in 10 mins before the guards arrived !
That was a few years ago and since then he has gone the Rothweiller alarm route ! No discount from the insurance co. but he's never had a breakin since.