Marco Tempest introduced a swarm of drones in his magic act by on Britain’s Got Talent: Unseen. He claimed that 15 drones are able to pick up micro facial expression to guess the number in a subject’s mind.
He asked one of the judges, Amanda Holden, to roll a dice and hide the number and then join him on stage….
He counts from one to six, all the possible values the judge may have seen on the one dice that she rolled. Then three of the drones light up red…and of course the judges confirm that was the number on the dice..
Source: YouTube