Year Introduced: 2006
Sport: Tennis

Implemented to address a long history of disputed line calls, Hawk-Eye and Cyclops machines use a team of cameras and ball-tracking technology to accurately predict where a tennis ball has landed on the court. The technology has been a success thus far, with only marginal criticism coming from players and spectators. It was particularly influential during the 2008 Wimbledon final when Rafael Nadal used his challenges to overturn a number of key points, leaving Roger Federer visibly frustrated. Those cameras are lucky that Fed is noJohnny Mac.