There is significant risk of cruelty when using these devices. In Australia, the RSPCA strongly recommends against them. They are controlled by State legislation here, legal in some States, illegal in others.
In my State, Victoria, they are legal only under specific circumstances: (a simple summary):
A person must not use a containment collar on a dog unless the person has ensured that the dog is trained to the use of the containment system and collar by:
<ul>
<li>a veterinary practitioner, or a qualified dog trainer.</li>
<li>A person must not use a containment collar on a dog unless there is a visual cue (such as a fence, posts or flags) that clearly indicates to the dog the boundary of the containment system.</li>
</ul>
A person must not use a containment collar on a cat unless the person has ensured that the cat is trained to the use of the containment system and collar by:
<ul>
<li>a veterinary practitioner or competent trainer.</li>
</ul>
A person must not use a containment collar on a cat unless there is a visual cue (such as a fence, posts or flags) that clearly indicates to the cat the boundary of the containment system.
there is more detail for the requirements in the Prevention of Cruelty to Animals Act.
Because of the requirement for visual cues, they can't be so-called "invisible fences." You must at least have a row of flags or posts.
There are also requirements that control the maximum electric shock, the spacing of the probes on the collar, and the collar can only be fitted to the animal for a maximum of 12 hours in any 24 hour period.
Personally I hate the idea of them. If you can't have a decent physical fence, or an enclosure, then don't have a dog. (or cat.)
I have seen RSPCA images of the wounds inflicted on animals when these collars become faulty - they can fail and start shocking constantly. It is nasty.
Our cat is never allowed to roam, he lives indoors and goes to his outdoor enclosure for a couple of hours a day, he likes to watch the birds through the wire.
