Years and years ago, I worked as a live-in maintenance man of an apartment building in what was considered a ‘bad’ neighborhood. And for a while, it ***was ***a bad neighborhood. I was getting broken into on a regular basis. Until I got a Doberman. Then it all stopped. Completely.
My tenants would jam a pair of cheap stockings down the toilet and while I was up in their apartment fixing the toilet, one of their ‘associates’ would be down in my vacated apartment, robbing me.
This is it. I can tell if someone is walking down the street toward the park and where they are on the street, by tracking the sound of the dogs barking. I wouldn’t try to rob a house in my neighborhood. There’s so many dogs, it’s like the whole block has an alarm system. If you get all the dogs in the neighborhood barking, some human is going to look outside to see what the ruckus is all about.
Anyway, after sufficient family-dog bonding, most dogs will bark to guard/protect their territory/den/pack anyway. I’ve never had to or tried to train a dog to alert me when someone is approaching my house. They all bark their heads off.