I have two teenaged cats who have been indoor-only their whole lives;
however, I recently moved to a house that has a nice, enclosed patio
that they love to play in.

Unfortunately, the fence, though quite high, is made of latticed wood.
They haven't scaled it yet, but there are cats that sit outside the
fence and taunt them, and they are close to figuring it out! I don't
want to deprive them of their outdoor fun, but I certainly don't want
them getting out, either.

I'm only renting, so I can't reconstruct the fence or add wire on top
of it to make it truly cat-proof. I was wondering about those
electronic containment systems, where you create an electronic
boundary, and then the pet wears a collar that gives them a little
jolt if they stray beyond it. I'm not thrilled with that, but I'd
rather that than either deprive them of the patio or risk them scaling
the wall and taking off...however, I've been looking on PetSMART and
other places, and those systems seem to be dog-only. Does anyone make
one for cats, and/or does anyone know of a cat-friendly system that
could help in this situation?

Many thanks...