So what I mean is if you want it to be like the Holograms app where you can see it from the "Home" screen then that is not possible. So basically, the Holograms app runs on the HoloShell, and allows the user to place them on their "Home" screen, where you launch apps from. This is currently not possible.
If however, you want to make a fully immersive app, something like RoboRaid, where you leave the "Home" screen and all you see is the app that is loaded then that is completely plausible.
As far as making a UI, User Interface, I would take a look at some Unity tutorials here: