samsung phones/tablets have a thing called "Smart View"... you can view your phone on any(?) smart TV and vice versa...
Isn't the viewing party a solution you can use?
Believe netflix has/had it
If you have Samsung, their app let's you copy either the audio or screen at the same time already. I use it when it's loud but don't want to turn the TV up, just have audio go through it as well and put it behind me on back of couch. Poor mans surround sound.
Install zank remote on both the tv and the tablet and you have this option
A guy on youtube showed it is possible with Samsung TV / Phone/Tablet
https://www.youtube.com/watch?v=GEruJ7PDn-I