Shirt sponsorship is a big moneyspinner in many sports, so flexible LEDs built into the jerseys could show different advertisers. It might be a bit distracting for the players if they were changing all the time, so perhaps they could change at every break in play -- or advertisers could sponsor specific set pieces. Imagine how much advertisers would pay to have their logo appear on the kicker who converts the winning points.
Rugby is a tough sport. A concussion-detecting helmet could use sensors to feel when a player has taken a big hit to the head, allowing medical staff to spot injuries. A version of this called the Reebok Checklight is already used by young American football players.
Ah, the joys of the gumshield. Many the schoolboy's dentistry has been saved from obliteration by the humble gumshield, but imagine if your slobbery rubber mouth guard could also sense your hydration levels and other important biometric data too.
It might seem like a brutally simple game, but there's a lot to think about in rugby. A contact lens with a heads-up display could help players make split-second decisions by highlighting gaps in opponents' lines, showing angles for kicks or passes, and showing distance to the try-line. If that's not too much like cheating, obviously.