This may be a pretty difficult one.
I assume that most HA users are using ras pi 3 as their controller. Since the ras pi 3 has an hdmi port on it, it would be really cool if there was an addon that gave us the ability to plug our controllers into our tvs so we can control our homes on the big screen via a remote of some sort (maybe this? or this).
This way, we could set up automations such as when the doorbell is rung and you are watching a movie, it could pause what your watching, change to the HA controller input on the tv, show you your front door camera feed for a few seconds, then change back to your show input and wait for you to un pause.
Also, would be cool just to be able to switch to your controller input to view camera feeds or album art on your tv.
Seems like this is possible already, if you put all the pieces together.
You just need some way to get the remote commands into Hass, some way to control your TV input, and something to display on the TV.
First two parts are easy in Hass with existing components.
Many people here use the Fully Kiosk app on tablets http://www.ozerov.de/fully-kiosk-browser/
It is nice because it has an API - ie. HA can control it and what it’s showing. I wonder if you could install Android on a Pi (or something similar with HDMI) and use it as the display device.
It seems feasible for a Docker image on Resinos to control the screen and show a GUI.
I found this guy that set up a minimal python web view to show a Flask based interface, it seems a scenario similar to our needs.