Having few minutes of free time, and 2 cats looking at me suspiciously from the other end of living room , I made a simple toy using laser pointers and servos. They actually played with it for few minutes – success 🙂
Arduino Uno, servo (micro 9g), 5V laser pointer and kitchen paper towel roll is all you need to make those.
Or you can expand on this idea and add a camera, microphone + speaker, automatic snack dispenser, internet connectivity to be able to see and play with your cat remotely and you just may arrive at a commercial-worthy solution 🙂 (like this one)
YouTube video – Ace playing:
YouTube video – Candy playing: