I ended up writing this (my very first SmartApp ever!) because I couldn’t find similar functionality anywhere else, or make other modules like Smart Lighting, operate the way I intended.
My problem statement:
Occasionally, family members forget to turn off the toaster oven, and as a result it has been left on for hours accidentally.
Solution:
Put it on a Samsung Smart Outlet and figure out how to get SmartThings to turn it off when it’s been left on too long!
Details:
The application I wrote looks for continuous usage over a pre-set time interval. With a toaster oven (my specific use case), when on, it consumes >400W, but when it’s on but idle (at temperature) it drops to 0.1W (but still above 0W!). I am looking to shut off the outlet if the continuous usage exceeds 20 minutes. Since that’s my specific case, I actually made these the default values in my code, but they’re customizable.
Like I said, this is the first SmartApp code I’ve ever written, so be gentle. 
/**
* Copyright 2019
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is distributed
* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License
* for the specific language governing permissions and limitations under the License.
*
* Energy Allowance
*
* Author: Dan Jeuch
*/
definition(
name: "Energy Allowance",
namespace: "djeuch",
author: "Dan Jeuch",
description: "Shut off an outlet based on continuous power draw over a pre-determined time interval. Example: Shut off a toaster connected to an outlet if left on for 20 continuous minutes using 0 watts or more",
category: "Green Living",
iconUrl: "http://cdn.device-icons.smartthings.com/Appliances/applicances15-icn@2x.png",
iconX2Url: "http://cdn.device-icons.smartthings.com/Appliances/applicances15-icn.png"
)
preferences {
section("When power is being used...") {
input "theOutlet", "capability.powerMeter", required: true
}
section("Turn it off after how many minutes?") {
input "minutesLater", "number", title: "How long?", required: true, defaultValue: 20
input "usingWatts", "number", title: "How many Watts? (0=any power)", required: true, defaultValue: 0
}
}
def installed() {
log.debug "Installed with settings: ${settings}"
state.InUse=false // InUse is held static to keep track if power is being continuously drawn
subscribe(theOutlet, "power", outletInUseHandler, [filterEvents: false])
}
def updated() {
log.debug "Updated with settings: ${settings}"
state.InUse=false
unsubscribe()
subscribe(theOutlet, "power", outletInUseHandler, [filterEvents: false])
}
def outletInUseHandler(evt) {
def meter=evt.value as double
if( meter > usingWatts )
{
log.debug "Outlet ${theSwitch} power: ${meter}"
if (!state.InUse) { // if this is a new power draw
state.InUse = true
state.StartTime = now()
log.debug "Energy Allowance Timer starting"
runIn(minutesLater*60,"outletInUseTimer",[overwrite: true]) // need to schedule this in case power utilization doesn't change enough to trigger this particular routine
} else {
def elapsed = now() - state.StartTime // in milliseconds
def elapsedSeconds = elapsed / 1000 // in seconds
log.debug "Energy Allowance Timer running at ${meter} watts, continuously running over ${usingWatts} watts for ${elapsedSeconds} seconds"
if (elapsedSeconds > minutesLater*60) {
log.debug "Energy Allowance Maximum time reached - shutting off outlet"
theOutlet.off()
}
}
} else { // if we are here, utilization dropped below the threshhold, so we reset back to the full time interval for the next time
state.InUse=false
log.debug "Energy Allowance Timer stopped - below ${usingWatts} watts being used"
}
}
def outletInUseTimer() {
def meter=theOutlet.currentValue("power") as double
log.debug "Energy Allowance Timer triggered, outlet ${state.Inuse} and using ${meter} watts"
if (state.InUse && meter > usingWatts) {
log.debug "Energy Allowance Maximum time reached - shutting off outlet"
theOutlet.off()
state.InUse=false
}
}