There's just one problem with these
The only problem with these is that they're invisible to delivery people, or other visitors.
When I was a yute, I used to deliver pizza, and I remember this one house in Wildewood that I came to. There was no warning, or info on this house, and when I got there, here come these two humongous dogs - don't remember if they were rotweilliers or german shepherds, or what - I do remember hauling ass back to my car, and driving away.
I called them a few minutes later, and told them that I'd have their pizza whenever they put their dogs indoors.
They basically said "Don't worry about it, just walk up to the door".
I basically told them, "Not a ####ing chance."
Then they explained about the electric fence.
Those dogs stalked me right up the sidewalk, up to the front door, but they never crossed the line.
Our fence was an "extra-strong top of the line model" and you could control the warning the dog gets before the actual shock comes but a determined dog doesn't care. 
My sister's does that. The dog stays in the fence for anything, except for when my sister or her husband walk off the property (across the street to grandpa's, the car, anything).
Now that's an idea!!! 
