Most animals will steer clear of capsaicin, the stuff in peppers that makes them hot. You can make your own by brewing up a hot pepper tea or use 2 tbsp of hot chili powder to a gallon of water. Add a few drops of castille soap or vegetable oil and mix well. Allow to stand overnight, then spray on affected plants or problem areas. Will need to be reapplied weekly or after strong rain.

To keep cats out of planted areas, you can also use orange peels or other citrus. Again, these will need to be replaced fairly often. Or use crumpled up chicken wire in between plantings.

Capsasin has a good reputation for repelling all kinds of animals, & it's non-toxic.

Whatever you use, be prepared to re-apply;
nothing short of atomic fall-out lasts forever!

Best way to keep your cat inside your "perimeters" is to keep him/her indoors.

There are just so many, too many, potentially fatal hazards out there:

dogs
other cats
cars
anti-freeze (fatally toxic)
heathen kids whose parents give them bb guns for their birthdays
the parents of those kids who think of cats as something like rats or vermin & who will shoot/poison/run over them
in some areas coyotes, bobcats, raptors
poisoned rodents-the poison stays in the rodent's body & poisons the animal that eats it.

Cats do like to be outside, & you can accomodate them:
it's very easy to build them a "cat habitat", like a gigantic plant window, where they can be outside yet protected.

I use one of these. They work great.

Please don't use capsaicin. Although it is non-toxic if ingested, it can still cause MAJOR issues if inhaled or if it gets in the eyes. This can affect your cat, too. Cats are not deterred by capsaicin until they inhale it or get it in their eyes. And by then, you have a very upset cat that is in pain. Which isn't ideal.
The best way to keep cats out of your yard if they are getting UNDER the fence is to use some of that cheap plastic trellis mesh (no clue what it is really called, but it comes in a roll) and staple it to the bottom of your fence around the perimeter.
Another option, if they are jumping the fence to inside your yard is to add motion sense sprinklers (or motion sense noise makers) on the outside perimeter of your fence, not inside your yard. These attach directly to your hose. The Scarecrow is one brand of motion sense sprinkler. You shouldn't have to do this permanently, but only a few weeks until the cats get the picture.
Cats will also avoid jumping over a surface if it has a 45 degree angle overhang. Basically, if they cannot see that they can successfully land on what they are attempting to jump on, they avoid it. An example of this type of overhang is linked.

Here is a link that might be useful: 45 degree overhang on fence

Yes, PLEASE do not use capsaicin. As said above it only works on close contact and once in the eyes it is extremely painful and animals can damage their eyes by trying to rub it out. It's going to act that way on squirrels and rabbits and other critters too.

Oil of peppermint has worked for us to keep critters out of planters. It smells strong from a distance so critters are much less likely to get it in their eyes and being an oil is less likely to fly up into their eyes if they dig beside it. Spreading it around a whole yard would be expensive but no more of a chore than capsaicin as both would need to be refreshed after rain, watering or a few days or so.

We find our own cats and the dog keep most others out of our yard but only when ours are outside. They are only out daytime with us, never at night, the strays come at night.

Things to try that will be set off by motion are: lights, water, bells. They'll all drive you nuts with their going off at night.

No capsacium - for reasons already mentioned.

Also for the reason that its more effective to deter the cat before it does anything, instead of retroactively punishing it (may or may not make the connection).

If youre concerned about cats peeing in your plantings, lay down thick COARSE mulch, and/ or stick in stakes that are about a foot or 2 high (those thin green bamboo ones are good) at regular intervals so cat doesnt have enough room to sit/squat.