I like your idea and really appreciate the goal but I also have the concern that using the app on your glowing phone might just add to the distraction.

Maybe if the user loaded the app and registered before the movie started, they could keep it in their pocket, unlock the phone, tap an area of the screen, and receive a vibration pattern as feedback that the theatre has been notified? It would leave the usher to determine the problem, but could reduce the "glow" annoyance. Just a thought. Best of luck.