During a recent presentation at the Tokyo Game Show, Xbox senior director of product management and planning Albert Panello fielded a question about the Xbox One's HDMI-In feature to support a feed from any device - specifically, the PlayStation 4.
The executive sidestepped the question at first but revisited the scenario a bit later in the presentation. He said any application can be snapped to a game which includes the live TV feed, so if someone wanted to play Ryse and Killzone at the same time, they could. If you aren't familiar, Killzone is a PlayStation 4 exclusive.
Up until this point, some believed the Xbox One might try to block the PlayStation 4 signal despite the fact that Microsoft said any HDMI device would be supported through the input.
So in theory, one could play a PS4 game through the Xbox One. Yeah, that's pretty neat but what's the point? I can see the practicality of using Skype or even having a football game or something playing alongside a game, but playing two different games at the same time isn't terribly useful. Both users would have a smaller screen to work with and only one would get sound through the TV.
It all reminds me of the Picture-in-Picture feature that television manufacturers pitched for the longest time. Sure, it was neat to watch two shows at once but other than to test it out, I suspect most people (myself included) never used it.