I need a GPS dot or some sort of cat locator...?

You want a GPS thing like the one in the DaVinci Code?

The button sized thing which somehow tracked him to within a few cm while inside a building that was shielded against radio transmissions and used some sort of magical power source because it was smaller than any battery that would power that sort of equipment for more than a few seconds?

That's easy, all you have to do is live in a movie where the rules of physics don't apply.

In reality something like that is about 2" x 2" x 1" minimum, needs the batteries changed every hours to ever few days depending on the update rate and costs ~$30/month to operate.

The technology you mentioned would be unrealistic. First, they would be very expensive. Second, it might even irritate your cat. The closest thing to what you're looking for is a chip that most people inject into their pet so that if they get lost, they can be found and re-identified. You could try and use a very small webcam type camera if you want to actually see what he is up to, but honestly I never heard of affordable technology for examining the adventures of one's cat thoroughly. I mean, there might be something out there that I missed but I don't think there is something that intricate.

Why no longer just maintain your cat inside. And do not say that is merciless, considering it's cruel making them live or keep external. Cats reside longer and have less sickness when stored within.