Very nice work on your piston, @Fe2_O3. Fun to put these things together.
To be frank, I’m probably not going to try your piston just because I spent so much time pouring through my device log looking at washer wattages that I just can’t bear to go back into it to see if I could find the values that might work w/your piston. The time I’m using in my washer piston works perfectly for us, so I’m going to leave well enough along for once. 
I have updated my pistons, and you might enjoy including a looping reminder I added, as I found that one notification was never enough w/my family.
I’m using a new service/smartapp/DTH combo created by @ghesp to do my announcing via GH - if you have a way to run node.js on an existing computer (or get a Pi Raspberry for <$50) you could integrate voice announcements on all the GH in your home. Or just remove those lines from the piston.
If you want to look at it see below. It is my absolute favorite ST integration to date…getting voice announcements on all my GH (and auto pause/resume music if it’s playing) is both very useful/effective, and absolutely cool. 
Anyway, here are my current pistons, Washer monitor/looping reminder and Dryer monitor/looping reminder. I use global variable so I can hand off between the monitor and looping reminders. I can’t remember who had posted their own looping reminder pistons that led me integrate a version of that myself, so unfortunately can’t give them credit.
Washer Monitor
Washer Looping Reminder
Dryer Monitor
Dryer looping reminder
