The sensors use the size of the creature to determine if they will turn on. So yes any thing the size of a cat can turn it on.

Here the rare flying squirrel seldom goes to ground. I would wonder if you have checked your local health department concerning the amount of West Nile you have in your area? The winter after West Nile hit here I found all kinds of squirrel bodies at the foundation of our house. No idea why they died there but none of the bodies that were not yet decomposing showed any sign of trauma.

The only motion sensor sprinkler that will spray the cats and not spray anything else is you holding a hose, sitting there on the porch keeping watch.

I suppose a few communities might have a law about free roaming cats, but it is not common. You can call your local animal control officer and ask if there is such a law in your town.

You can always set havahart traps on your own property and haul the loose cats off to the pound.

Perhaps the owners will keep them inside after paying to bail kitty out of jail.

More than likely, though, all they will do is to get another kitten when their cat doesn't come home.

I've worked in an animal shelter and virtually no one ever came in to reclaim a lost cat. A very few had owners come for them. A few more got adopted, and a huge majority of them were put to sleep because nobody wanted them.