For several years now, National Football League officials have worried that watching a game on TV has become so much fun that people will start to prefer it to a trip to the stadium. Its solution, it seems, is to co-opt the best of the living room: wire up stadiums and make sophisticated mobile apps to mimic the sensory overload that comes from scrolling through a smartphone while flipping channels at home. In an ideal scenario, teams can connect with fans via apps that do everything from stream highlight reels to monitor the length of the bathroom lines. About 20 NFL stadiums are already Wi-Fi-enabled; the league recently told the laggards they have to get up to speed within 18 months.