Two way light for meeting indicator?

Is there some kind of device my wife and I can use to indicate when we are on calls? We both work from home so something like this would be helpful.

Would be great if I could have some kind of light in my office that says “on air” “off air” or something to let the other know when the other is on a call. Like if there could just be a button in her office she’d hit when she’s on or off a call. Then we could both have one and let each other know easily.