Source: http://gizmodo.com/world-cup-refs-are-wearing-smartwatches-that-alert-them-1589886222
At today's opening match between Brazil and Croatia, the referees will be wearing smartwatches that read "GOAL" and vibrate when a team scores. No, it's not punishment for the infamous Frank Lampard disallowed goal of 2010. It's part of a new "unhackable" goal line detection system, the first to ever be used in the World Cup.