A small, powerful microcontroller card. It is small enough to be added to any project already built and cheap enough to be used without hesitation.
It's a tiny microcontroller board, built around the Atmel ATSAMD21, a little chip with a lot of power.
Adafruit Pro Trinket - 3V 12MHz (Compatible with Arduino)
Pro Trinket combines everything you love about Trinket with the familiarity of the common core Arduino chip, the ATmega328.