This is a demonstration of the Photons publish and subscribe features. When the photon publishes an event to the cloud it makes that available to other devices that have subscribe to the event. The other devices is not just limited to other photons but could also be internet connected smart phones ore web browsers.
This is a simple LED clock I prototyped following Simon Monks post. I am using a Particle Photon, a couple 4.7k resistors and a 7 Seg Display with an Adafruit I2C backpack.