The Economist has an article on a Canberra based company GPSports Systems and their revolutionary work with football:
GPSports is pushing even further, developing an integrated alert system to send a beep to a referee’s earpiece within a quarter of a second of the ball going out of play, passing between goal posts or, in rugby, traveling forward from a pass, something forbidden by the rules of the game. Mr Hawes says the ball’s location can be determined to within 1cm, and expects to test the technology early next year.
Exciting times.