As I've been selected as one of the finalists in the IoT Holiday Lights road test, it's probably about time to put some firmer plans in place. My core idea is to take the readily available RGB LED strip lighting found (among other places) on Amazon and use them to construct Christmas globe-style ornaments.
This is a quick and dirty sketch of my concept:
What you see there is a 3D printed core with LED strip lighting wrapped around it, with a 3D printed shell to fit over this core and act as a diffuser. Moving beyond the basic concept, the outer shell can relatively easily have additional words or symbols or patterns added, but that can come later.
Each ornament will have leads attached which can be used to daisy-chain them together in order to cover an entire tree (or as close to it as the power limitations of the driver board will allow for). These will ultimately connect back to the main driver unit, made up of the Yun and Infineon LED Shield, which will in turn connect to a local network in order to be controlled.
The precise mechanism of control has yet to be decided, but some ideas include the simple "RGB colorwheel with the ability to add cycling presets", the more complicated "tweet to control" interface, or the "change color in response to incoming emails/twitter messages/facebook notifications/etc" to turn the entire tree into a notification LED. One interesting option with the "tweet to control" interface is the possibility of setting up a public webcam as well as a publicly visible twitter account which will accept @messages containing hex color codes to set the LED colors in order to recreate the once popular automated christmas light house which internet users could control and watch via webcam.
Once the basic ornaments are completed, the more advanced control options can be explored. Lots of possibilities... this one should be fun!