Cat herding, it is possible
 

After about one month experience... With very limited use, and not actually
shocking anything (of course), just the sound of a stun gun can be an
extremely effective tool for convincing your cat to do something or stop
doing something.

Currently one of my cats is on the porch. She can also climb up on the roof
and have fun up there, chasing birds and watching everything go by from a
safe vantage point. And she does enjoy that. But sometimes she goes out of
the area. There is a local tomcat that beats up on her when she does.
Besides, she is stupid about people and could easily get killed. She is not
a street kitty.

Of course she doesn't listen to a word I say. It's like she's deaf. But she
turns into an extremely obedient kitty when she hears the stun gun. I don't
even have to fire it now, just showing up on the porch with the stun gun in
my hand makes her run back. It might even stop her from wondering in the
first place (to be determined). And of course as she's hightailing it back
I say "good kitty" and all that stuff.

Could be useful inside too, if it didn't freak out all of my cats. In a
single cat household, you might teach a cat not to do things simply by
using the sound of the stun gun. But one would have to be very responsible
and use it only for specific things. It's an amazingly powerful deterrent.
Probably works on at least 95% of cats. But definitely should not be used
inside with more than one cat.