What can it rule on?Line calls. It is most commonly used on the service line with serves regularly topping 220km/h, that would test the eyesight of the most ardent carrot eaters.Players get two incorrect challenges per set and at most tournaments the expensive technology is available only on the show courts. What has it done for the sport?It has taken most of the temper tantrums out of the game and it has undoubtedly improved the accuracy of calls in the major tournaments where it is in play (you only have to make a trip to Auckland's Stanley St for two weeks in the New Year to see plenty of reasons why HawkEye is a good thing).Because the information is available instantly, there is no delay and at the US Open in particular, the crowd find the anticipation that builds during slowmo images on the big screen almost as entertaining as the match.It is not universally popular however.It is believed that similar incidents have occurred in the Lusby area but involve victims who may be re