[llduxcao] Self synchronizing clocks

Deploy a bunch of devices which communicate via radio to synchronize themselves to the same clock.  Master-slave would be the obvious set up, but consider making the problem harder by assuming that no one device can "see" all the others.  We need a distributed network.

Inspiration was a set of LED party lights which change color in sync.  They offer the possibility of communicating with each other by light instead of radio.