I made a simple ON AIR sign with LEDs inside that I change to reflect what I was doing. Red means I am in a meeting or totally focused, blue means I'm working, but someone can interrupt me if needed. Green means I'm not working, come on in!

The only issue with my setup- I work from home. My wife does not. No one is there to care if they can come in or not. It was building something fun to solve a problem I never had.

Would do again.