Works!
At first I thought these were probably not ethical. However, since the working parts of the citronella spray seemed to fail me, I thought one without moving parts might be better
It gave my poor dog a little fright - however I believe its not like an electric shock as we know it - more similar to the electric pulse machines you can buy for pain relief from the sports therapists.
She doesn't bark anymore, so it doesn't actually do much except sit around her neck. She doesn't set it off now. To me, her reaction was the same with the citronella collar - gave her a surprise and she stopped barking. I think they are fine and they learn pretty quick.
One happy owner and dog