"In a Meeting" Headset Sensor

I work remote, and I made this to have a sensor to let people know when I am on the phone so as not to barge in the room. This works by just making a headset holder and I put a button inside. When the button is pressed (headset is at rest and unused) it tells a light in the hallway to turn off. When I take the headset off for a call the button is unpressed and the hallway light turns on.