The app which is an extension to the TV Catchup website, streams all the Freeview channels to your device if you dont have a box or dont happen to be at home. Whats nice about the interface is that you can see what else is on at the same time as watching a channel without having to change screens. This is something only the 4od app features. I find this app useful as i dont actually have a TV in my bedroom anymore. Its free to register and you can use the same account on your computer or laptop.