Well I tried Binging it and I also couldn't find anything. I'm guessing it's having two apps open side by side. It might not be because although it would work great on the 1520, it wouldn't be so good of a feature to have on a small screen like the 520.
I'm pretty sure its an app from Sony. Its already on Android and IOS and it allows you to use your phone as a remote for your TV. It also allows you to check TV guides. I don't really see what it brings to the table cause there are other apps that do the same thing out there. Anyway that's what I found on google