The Arduino Christmas jumper has been created using an Arduino Uno, Arduino Mega, and Adafruit Flora development boards.

Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. Anyone interested in creating interactive objects can “play” with Arduino! Described ...

The build makes creative use of a pair of Christmas ornaments. They are perhaps the cheapest and easiest way to source a clear plastic sphere.