Single Status Update
Steam beta has a new feature that lets you play with other people as if they were also there, using the same input systems as you. Shared keyboard/mouse/controller.
More info at: https://steamcommunity.com/games/593110/announcements/
Downside is that it only works for games that are flagged for local coop and have had the a-okay from the publisher to let it be done.
Well, that's the alleged restriction.
Steam games need some magic applied to function, but non-Steam games are very easy to do.