While users certainly have their phones and tablets turned on as they watch TV, there hasn’t been a killer second-screen app to gather them all. There are some good contenders, however:

There are plenty of guide and discovery second-screen apps for TV, but Peel stands out due to its relationship with specific shows. “American Idol” viewers last season were able to virtually “cheer” or “boo” both the performers and the judges — with a weekly score card summarizing the results, adding to the social experience.

Launched in 2008, this Foursquare-like app is the leader of TV check-ins, with more than 3 million users. Such networks as HBO team with the service to reward superfans. Frequent users are rewarded with virtual (and, in some cases, real world) stickers.

Launched as a music discovery service, Shazam has moved into TV in a big way, letting users download “how to” videos during a Home Depot commercial or giving fans of “WWE Raw” the opportunity to watch exclusive video or buy tickets and gear.

Yahoo!’s TV companion app identifies shows and movies from its audio fingerprint, offering contextual stories, Tweets and real time discussions with others watching at the same time.

‘Wreck-It Ralph’ apps show power of small screens