So you would like to make your own wearable, Arduino driven animatronic tail for your next cosplay event? circuito.io has shared a guide that shows you how to do just that. You are going to need Arduino UNO & Genuino UNO, SparkFun triple axis accelerometer, analog joystick, and servos to pull it off.
Knowledge of 3D printing and Arduino programming is ideal. More info is available here.