The BlinkM by ThingM was the original pixel addressable LED. Instead of the serial protocols we use today, the BlinkMs are I2C devices with their own microcontroller and super-bright RGB LED. They support all kinds of commands like set a RGB or HSV color and fading. A really cool feature is that they can be scripted with a tiny script stored in the Micro's flash memory so they can perform animations with just 5V power applied.

I used these in a costume and after a few years of storage I removed the BlinkMs intending to use them in another project. But that never occurred and probably never will so my loss could be your gain. I originally paid something like $12-15 each for these (remember they were the first!) but letting them go for super cheap now.

See the link below for the manufacturer's page.