The best actual Rube Goldberg illustrations had things like steaming kettles and animals as parts of them, not just marble runs. Clever as those are.

Automatic Cat Feeder and Reminding System:

Step one, acquire cat.

Step two, train cat to free-feeding. This is a critical step.

Step three, acquire dry pet food dispenser
An inverted container holding up to two weeks' worth of kibble. It is a simple gravity activated device. Cat eats food at bottom, more food lands in dish.

Step four, pet trains you.

Step five
At 6 am this morning my cat knocked my cell phone off my dresser,

Step six,
causing it to chime "goodbye!"

Step seven,
waking me from a dream in which I was trying to design a Rube Goldberg device for this task. I'm not making this up. (The dream involved a birthday candle and a pulley system and a paper lantern structure that floated off into the sky. Which is I suppose technically possible.) Cat wakes me up out of a sound sleep every two weeks or so with some form of precussive instrumentation (change container knocked off dresser was the most musical) in order to remind me to refill her feeder. Yes, I am a bad cat mommy. And I need to buy more kibble today.