HawkEye is the proven system to date. As it seems to recognise the difference between human traffic and a ball. No system though is going to be infallible. My understanding is that with any of the systems under test it only takes maybe nanoseconds for the signal to engage. I think they will have to test it for a season or so just to iron out any pitfalls. I have to say though that the chip in the ball would be my choice if it could be proved that kicking the hell out of the ball did not adversely affect it's efficiency. The reason I say that is because it could be used on the byeline as well. Although it still wouldn't be able to tell you who the last one to touch the ball was!