As someone who's been in the business but got out, I wanna know what hasher might suggest. I won't even pretend to come close to the sheer $$ amounts of his jobs, but I've designed a few fairly impressive ones myself. Installed some real wild ones for a couple of people who were s#!$ magnets and had the money to pay for whatever they wanted.
I have to agree with hasher on the wireless panix and I would suggest a fogging system that *YOU* control. The ones tied into your alarm panel are not idiot proof and a few of them I've seen weren't even idiot resistant. They do work wonders at a business at at home (if you control them) though, unless one of Tom Clancy's Rainbow Six teams is knockin down your door.
If you are really serious and have the money to spend, cell backup has become very affordable. There are great systems that actually centrally monitor the sonic activity in the building when the alarm is tripped. I never wanted someone to have the ability to hear what was going on in my home/business if one of the kids set it off by accident or one of the Danes tripped a "pet sensitive" detector. All that stuff gets recorded - can you imagine the laughs the monitoring guys are having when your dog sets off the alarm in the middle of . . .
As for outside PIR/motions - there are some good signatured detectors out there that can determine the difference between a cat and a cat burglar, but anything over ~ 75 lbs confuses it, and they have to be set up correctly. And hasher is on target with the cold climate stuff. Extremes in temperature have a tendency to play tricks on PIR/motion detectors.
If you have a big enough place (and the $$$), privacy fence with a couple of loyal, trained canine helpers who can't be drawn away with food or another dog (get a couple of females - they could care less about another bitch in heat). Just remember, there are lots of ways to disable a dog if someone is intent upon accessing your home/business/loved ones. Full perimeter alarm with glassbreaks and PIR/motion/signatured detectors as backup. I like alarm screens myself, but that's some serious $$$. My cost was $50/each a few years ago (as an insider in the business), but if you cut or remove one the alarm is tripped.
Shoot for exterior strobes to silently alert the neighbors/LEO/first responders. These can be mounted anywhere on or in close proximity to the structure. I've done a series of them down the driveway (looooong driveway) in a rural setting to show the way to the house.
Do the full fire protection system.
All the rest I think I laid out pretty well if you are designing from the foundation up during the discussion. Several others had some wonderful ideas - I like Bogies about the hidden spirals, but hey! I'm just the kind of person who would build something like that just say I did it!
Oh yeah, one more thing. Don't start shooting until you have to and don't stop until the threat isn't any longer. Then, look for other threats.
ERRainman