Go don’t have a HomeKit device with power meter so I can’t say for sure if this works: you could create a rule in the iDevice app that turns on/off a virtual switch based on the power level, and you include the virtual switch via Homebridge. You can then write rule for monitoring your laundry for the virtual switch In Webcore. It will probably work, but there are lots of opportunities for errors.
Have you considered just using something like the zoos zen15. They don’t look like clunky smart plugs. (i know they create a lot of z-wave traffic but they work great! 
)
http://www.getzooz.com/zooz-zen15-power-switch.html