Apple's "single sign-on" feature has only been live since mid-December but it's already attracted some impressive services. In addition to A&E, Bravo, NBC, Syfy and USA, which launched with the feature, WatchESPN added the functionality in January and, on Thursday, HBO announced that its HBOGo app will now support it as well.
While it does now sport some popular content providers, the single sign-on system hasn't, on the whole, been widely adopted yet. It requires both the user's cable service provider -- like DirecTV, Dish, SlingTV or CableONE -- as well as the app developer to implement support before users can take advantage of the service. That said, the addition of both ESPN and HBO are likely going to drastically enhance its appeal to users which, in turn, should entice larger cable providers (looking at you, Comcast and Time-Warner) to implement it as well.