The MLB general managers' meetings are underway, where several potential changes to the professional version of America's pastime are discussed. According to the New York Post's Ken Davidoff on Twitter, one of the changes includes an expansion of the league's instant replay system.
https://twitter.com/KenDavidoff/status/266363893251715073 Instant replay has been used by MLB since 2008, and then for a single purpose. Umpires can use video replays to determine if a home run is fair or foul, but not for other calls on the field. The NFL has used its current system of instant replay that allows coaches to "challenge" calls since 1999.