I built a physical version of this back when I was teaching HS math and science. I used two bicycle hubs, and attached metal arms to each. I put an LED on the second hub, and the end of the second arm.
For the demonstration, I'd have it under a blanket in the front of the room when students came in. I'd turn the lights out, only turn the outer LED on, and set it in motion. Then I'd cover it up, turn the lights on, and ask students to sketch what they thought was under the blanket. Then I'd turn the lights out again, turn both LEDs on, and set it in motion again.
Most people were able to sketch something pretty close to a double pendulum after that second demonstration. I also set up a camera and did some time lapses, and got pictures that look just like this online demo.
Super fun project, and students loved it! :)