Here is a smart system that enables your fish to break stuff around your place. The Fish Hammer tracks the position of your fish using a webcam and a software written in C++. It has a hammer that follows the fish around the tank using an Applied Motion stepper motor.
As Neil Mendoza explains:
The software calculates the velocity that the motor needs to be moving using a PID algorithm that takes the motor’s encoder position as input and gives a velocity as output. This velocity is then sent over UDP to the stepper motor. The hammer head drops based on the slow rotation of a cam that the hammer rests on.
This was designed using Autodesk Fusion 360 and Inventor. You can find the guide here.