The Pew Research Center's Internet & American Life Project has released The Rise of the "Connected Viewer".
Here's an excerpt:
Television's solitary screen is being supplemented by multi-screen interactivity. Half of all adult cell owners (52%) have used their phones recently for engagement, diversion, or interaction with other people while watching TV. The Pew Research Center's Internet & American Life Project measured the prevalence of these multi-screen viewing experiences by asking the 88% of American adults who are cell owners whether they had used their phone to engage in several different activities while watching television in the 30 days preceding an April 2012 survey.