I haven't used any power reporting devices so syntax may be different that what I type below, but I think the concept is pretty simple. In the cases below, it's important to understand that in RM, the actions only run when the true/false state of each rule flips. The (Cancel) notation in the action delay stops any pending actions if the rule's truth state changes during the delay. This works the same as the "stays" trigger in webCoRE.
As far as the WasherIsRunning variable...what's that used for? This may require some modification if the Thermostat device brings the power consumption back up over 7W when the washer is not running.
First rule:
Condition: Power > 50
Rule: Power > 50
Actions when True: Delay 1 minute (Cancel), Turn off Thermostat
Second rule:
Condition: Power < 7
Rule: Power < 7
Actions when True: Delay 3 minutes (Cancel), Send SMS, Turn on Thermostat
Here's a similar thing that may help and/or provide an alternative as well:
