I don't know about the cat friendly ant killer - I like Grants Ant stakes. I just try to put them where the cat can't/won't get at them, and close to where the ants are entering.
For the cat's sanity - she HATES ants in her food - I set her dish is a pie pan that has water in it. A moat for her food dish! This sometimes is enough to deter the ants from coming in - if there's no food for them.