This is a long article but well worth the read for the tech curious. Here's an excerpt:
For two years, Lambeau Field acted as a laboratory for what is possible in understanding the National Football League. During the 2009 and 2010 seasons, 20 cameras set up around the Green Bay Packers’ hallowed stadium were used to test the next phase of analyzing football.
Using optical recognition technology, the cameras tracked each player as he flew around the field, collecting information and quantifying what has long been a cliché thrown around the league.