Le Dominoux are “LED dominoes”, a blinking LED that propagates from device to device. Each Dominoux comprises a coin cell-powered 555 timer circuit configured as a one-shot, triggered either by a photo transistor or CdS photocell. Using a bunch of Dominoux enables creating various lighting patterns, trains, and continuous loops. Other Dominoux variants are the basic blinky for generating light pulses, and a tone generator for making annoying beeps.
Endless fun with LED dominoes – [Link]