This is a really difficult one, and I sympathise. My mum had 2 dogs, both quite young, and both well trained. She then had a severe stroke and was in hospital for 6 months. My sister looked after one and I looked after the other.
When she went home she took the labrador that I had been looking after and my sister kept the spaniel as we all felt that it was too lively for my mum and it wouldn't be fair on either of them.
Anyway, my mum lets out lab for fresh air and exercise - lab disappears (never having done so before) and is found by neighbour having killed a deer - oh my god. My mother is distraught, but desperate to keep her dog as she is her only company and encourages her to get exercise. So, after several similar episodes, although thankfully with no more deaths, she installs one of these electric systems. It has done the job - after a couple of mild shocks the dog doesn't stray and the system is now permanently off. It sounds brutal, and isn't ideal, but it is never just a case of black and white and I know how easy it is for a dog to slip away when you are busy with children etc.
For us to take the dog away from my mother would be a disaster for her, and when we had her here, the dog was miserable being away from her owner. In an ideal world we would all train our dogs to do exactly as we want, when we want, but we can't foresee what's going to happen, my mother wouldn't have contemplated using the system if she hadn't been ill, but if it's that, or a dead dog then I know which I'd prefer.
We use electric fencing for horses, cattle, sheep and pigs so why the disapproval for dogs - like all these things, if it's done carefully it can work. I'll put my tin hat on now!