My IoT button is stuck to the washing machine. It uses AWS Step Functions and SNS to text me an hour after it's pushed to tell me the laundry is done. Unnecessary? Completely. Useful? Heck yeah.
See for instance: https://philhawthorne.com/making-dumb-dishwashers-and-washin...
https://steve.fi/Hardware/washing-machine-alarm/
I tried using a microphone at one point too, but that was not as reliable as just taping a sensor to the back of the machine and alerting after movement stopped.