Comment by MisterTea

> The optical communication for the Miele was pretty interesting too. I'm assuming it's to prevent moisture from corroding a port of some kind.

IRDA was very popular at one point and still lives on in applications like these. It's an IR serial port hung off a UART. It's stupid simple requiring no cables, pairing, or complex protocol stacks. Some smart phones have IR blasters built in so its a total win for ease of deployment in cases like these.