I've given that some thought in the past. Is there a chip that is capable of recognizing the exact shape and size of the ball and be able to sense when one of the edges crosses a plane?
There are also multiple padded bodies blocking the signal much of the time.
Belichik or Tomlin would probably have one of their players have a chip in their pads to trigger it, lol.
There would likely need to be at least 6 chips inside the ball. One at each nose, and four 90 degrees apart from each other ringing the waistline of the ball.
You could easily prevent cheating like you suggest by each chip having a unique ID and the Refs scanning the chips into service when they put a ball out there.
Problems that would have to be solved include getting the chips to absolutely, 1000%, stay in place no matter what. Kicking, tackling, punting, etc.. CANNOT ever allow a chip to be dislodged. Also, whatever method you use to hold them in place cannot alter the balance and throwability of the ball. Lastly, it has to be 'manufacturable' and not cost $10k per ball.
After that, every field in the league would likely need something like a wire with reader chips placed at every yard marker buried at the edge of every boundary.
Standard RFID chips & readers could handle all of this, and signal strength from the chips in the ball measured at the most nearby readers would give pinpoint placement.