I connected a MPU-6050 gyro sensor to a NodeMCU ESP8266. It monitors the vibration of the washing machine, when it stops it sends a push notification and goes into deep sleep. code
The pin layout:
scl - d1 sda - d2 vcc - vin gnd - gnd
The push notification is sent with IFTTT over the maker (webhook) channel.
The project was inspired by Laundry Sensors with NodeMCU and Home Assistant.
Alternative you could tape a photocell over the ”done” light. Or put a power meter/power clamp on it, when the power drops it is done.