Stop Light Badge
A fun little badge that doubles as a development platform for NXP's KL03 low-power Kinetis microcontrollers and NXP's FXOS8700 accelerometer/compass chip. 100% custom laser-cut acrylic. Tap twice on the front (think Fitbit) to change into the six different modes. Three of the modes use blue LED's to accent the florescent yellow acrylic when in the dark.
Uses a single AA battery that can last many hours (10+).
Full SDK and design files available here.