Check out PIPS:Lab's "DieSpace" performance art, in which the audience participates by gesturing and drawing letters with LEDs that spell out words like their names, answer yes or no questions by nodding or shaking their head with the LED held to their forehead, and the gestures are recovered along with images of their faces, and reconstructed into their faces and names into a 3D Die Space Cloud! That was at least 11 years ago, but it's pretty obvious how it works, and how fun it is, which is why it works so well! You can see them automatically registering all the faces in the audience on the laptop on stage in real time during the performance.

Diespace internet community for the deceased HD:

https://www.youtube.com/watch?v=aQz_irTiqGE

PIPS: lab at TEDxAmsterdam

https://www.youtube.com/watch?v=ApyDSq_DbQo

PIPS lab Showreel 2017 @ 1:24:

https://youtu.be/FNzTWqraCDU?t=84