Looks to me like the app is supposed to play certain sky channels as well as giving you sky news and sky sports news feeds, however not found anyone who has got the videos working yet.
And for those Sky + users out there you can set it up so that you can record programmes via your phone.
It's description said that you can also access the full TV guide however when I was having a quick look last night I could not see this.
The app gives you a update of your data use when you close as well (which is quite good)