https://www.techradar.com/news/wearables-of-the-world-cup-what-the-referees-players-and-managers-are-sporting

Video assisted referees (what you'll hear refereed to as VAR) has been the one of the most controversial elements of the World Cup 2018, but it’s not the only tech that’s being used on the football pitches around Russia this month.

Wearable technology has come a long way since the last World Cup. Back in 2014, the Apple Watch was only a teaser announced on stage by Tim Cook and was yet to be on anyone's wrist, while watches such as the Moto 360, Samsung Gear S and Pebble Steel were among the bestselling smartwatches of the year.