Waytext is a simple Wayland program to display text to a user on all displays at once.
It makes use of the (currently) unstable layer shell protocol to render on top of other windows.
This is useful for notifications where the user should be more aware of them, for instance I use it for notifying me of when to take regular breaks. The fact that it overlays even over fullscreen windows is very useful!
Check out the projects page for some links.