I was staying at this hotel for work and I was convinced this was a motion-sensor split flap, since it never seemed to turn on until I rounded the corner into the elevator bank. The flaps make a very satisfying noise- a homage to the train station boards. There is a link to a video that I took below. According to the article posted below, it’s on a timer, not a motion sensor, but at the time, I thought it was a cool use of a motion sensor.