Many large concerts feature wristbands that light up on command. They are used to produce varied visual effects across a stadium. One company that makes these is PixMob. Their controllable, illuminated wristbands are currently being used as part of Taylor Swift’s Eras Tour. A short Wired article here gives some details.

John Graham-Cumming’s blog does a teardown of a wristband. It’s rather simple.

 

On that board are two RGB LEDs, a little microcontroller, a little bit of EEPROM and an infrared diode to receive a signal. So, simply put, PixMob works by installed a really big (and moveable) IR remote control (you can read about this on their website here) and transmitting commands to the bracelets to produce colours, fades, flashes, etc.  There are a bunch of hardware details here.

A Flipper Zero can send the correct infrared pulses to change the colors.

See the video below and more here.