I agree! I think it would be a great feature to be able to read if there are any observers of your chess game, whilst playing the chess game. For instance, in a team context it is useful to know, or even if chess friends are observing your chess game. would be useful!
How to know the observers of our game ?


Listing watchers might be practical if it's only a very small number. But I don't think you would want any notifications since avoiding distractions is always a priority.
You could always just become visible when the game ends. One list of who watched the checkmate, like how guess the move list the players who played.
Doubtful anyone watches games of an 1800
I try to watch players that are close to my skill level.
watching GM's play can be hard because I don't understand the 'why', of too many moves.
I'd say if you knew that there's a chance of people messaging those watching and asking for the engine lines... Just a caution.