Santiago Alfaro has been working on a project at MIT that I find fascinating, but also see tremendous commercial potential in. Called Surround Vision, the concept extends our view of television content to external handheld devices. If someone runs offscreen, holding a handheld device would allow the viewer to turn around and see where the person continues to run! Sort like adding a unique version of the story that you, as viewer, get to crop and control.
This project shows promise for making television truly interactive, as well as giving stories have unusual side plots, hiding Easter Eggs in the content and overall making television more enjoyable.