In the words of its creators, The Ides of DEF CON is a wearable hardware badge, featuring featuring blinky lights, sound, a sub-1Ghz radio, games, and more. Based on the NXP/Freescale KW01.
Article Link: https://blog.avast.com/ides-of-def-con-inside-scoop-on-best-unofficial-electronic-badge-def-con-25