Rather than zapping the pet, give it a good feeling when inside the zone.
This idea is about a leash that gives the pet a good feeling, and, using positive rather than negative reactions, causes the pet to stay inside the premises.
For a short training period you attach the feeling (which could be a sound or a mechanical patting) with good reactions from the owner. For example: Each time you give it some tasty food, or after a game you played with it, you activate the leash.
Now the leash is set for use. Just like a geo-leash you set the area where the pet is to stay. As it gets close to the inner "fence", there is a build up of the good feeling. But if it stays or moves towards the outer fance, the feeling dwindles. As it goes back towards the fance the feeling gets stronger. Once inside, a "reminder" is given every once in a while.
Perhaps an "upset" sound can be played, so the pet knows that its "loosing" - since it is leaving the area.
I read once that the polar bears in San Diego zoo sit in a place which is good for the visitors to take pictures, because they put the air conditioning outlets there...-- pashute, Sep 19 2010 [+] for not suggesting direct electrical brain stimulation.-- mouseposture, Sep 19 2010 Nice enough idea, but pets already get real, stronger positive feelings from their owners. Then as soon as another pet or person wanders by, they're off. All the 'soothing' sounds I can think of don't seem to work on a dog who sees a cat outside his premises.
Nothing works on cats.
Maybe if you got them addicted to some soothing drugs, this might work.-- Boomershine, Sep 19 2010 AFAIK geo-leashes usually work (according to Animals in Translation by Temple Grandin...) So these should work as well.-- pashute, Oct 04 2010 random, halfbakery