I'm a bit sketchy with the whole chip thing. Not sure why. I think I read too many sci-fi books as a youth or something. When I got my current dog, she was already chipped, and I asked my vet about removing it. He thought I was nuts. I probably am. For your application, it sounds like a great thing - cat in, all others out. My son had a raccoon get in his house through his pet door and it really created a mess, plus he felt as if he'd been burgled. Creeped him out.
