I hate to admit to this but I have one. I have two dogs, one is like Houdini, she can escape from anywhere. My property is fenced but she digs down below the fence and manages to squeeze through the smallest space. My other dog follows blindly, even to the extent of injuring himself trying to get through the same space as the smaller dog.
I have a large plot and cannot afford to re fence.
One day the dogs got out and went onto my neighbour's unfenced land and killed two of his Yorkshire terriers. He threatened to kill my dogs and my husband if it happened again. I belive they also killed a few cats on their trips out.
As a last resort, I bought an electronic fence and it has been a godsend. The Houdini dog needed only two shocks, before learning to stay put. The other dog who isn't very bright needed a couple more.
The shocks are not very strong, my husband tried it on his arm. I think they were more of a nasty surprise than anything else.
If the dogs had needed repeated shocks, I would have thought it cruel and stopped using the fence, but it did it's job, quickly and successfully. My dogs now stay in the garden and the neighbourhood pets are safe.