What if the clock on the wall in the room could also send a signal that it was time to wrap it up. The clock would be synched up to the room’s calendar so it knows what time each meeting is supposed to end and begin. As your meeting starts the background would be green for the first five minutes – meaning you should get started right away. The next forty minutes (of an hour meeting) it’s yellow. When fifteen minutes are left the clock background turns red so you know you should finish. Finally, at the five minute left mark it uses it’s built in motion sensor to know if you’re still in the room and if you are it sprays the room with water or something ridiculous.
Never let a meeting run over time again.