As far as i remember fallout 4 has this feature but poorly executed.
But i still see great potential
My idea :
I was developing a RPG Games with some very fresh idea. 1 of it,
May using Smartphone AS 2nd Screen + Custom Input.
the 2nd Screen would be like some game in nitendo DS
for input, extra menu, useful info.
How to :
Using Multiplayer Features:
PC = Host
Mobile = Client
Host = main game
Client = Different UI depend on main game status.
My Question :
Any possible Pro / Cons you guys may notice?