Which, truthfully, I would rather have instead of a system. But we have a little house, and two cats, and it's just not in the picture for right now. Next house, I want a dog just like my family's dog: a chocolate lab, just like Taylor. Best dog in the world (and I'm scared of most dogs!)
In the very rural setting of my parents' home, if I'm home alone, I have Taylor sleep with me, and stick around downstairs late at night. Friendliest dog, wonderful with my two little brothers growing up, but also very, very protective. With the younger boys particularly, if you're wrestling with them, Taylor gets annoyed and will put his mouth around the older aggressor's arm. No bite, but just a warning to back off.
Also can sense bad people. Story: dog hates some particular service provider guy, I can't remember which one. The guy didn't use the front door one time coming to the house, but came through the garage, which probably didn't help. Taylor got on his pissed face and blocked the entryway and backed the guy's ass all the way back outside. Supposedly is a nice guy, but Taylor does *not* like this punk. Which my mum says, maybe the dog is sensing something shady about him, I don't know.