Use a zwave (or equivalent) plug that can monitor loads and detect when the load is below a certain treshold. I have this for my dishwasher, dryer and washing machine. Works like a charm!

See for instance: https://philhawthorne.com/making-dumb-dishwashers-and-washin...

On the basis that washing machines always break one month after the warranty expires, next time you need to buy one, look for one that beeps and jingles when the program is finished. Mine does this, and it's loud enough to be heard anywhere in the house.

Motion sensor seems like the easy solution there. My washer dryer shake a lot when they're going...