BlinkMs are “smart LEDs”, a type of smart interface component. A BlinkM consists of an ultrabirght RGB LED backed with a microcontroller with built-in knowledge about 24-bit color spaces, color fading, and color pattern generation. All in a package 0.6” wide. You talk to it over I2C, a serial protocol spoken by many different things. (Arduino speaks it, as do Basic Stamps, and your PC) And you can have over 100 BlinkMs on the same serial bus, each individually addressable.