definition(
   name: "PowerSensor",
   namespace: "mschilli",
   author: "Mike Schilli",
   description: "Subscribe and detect",
   category: "Convenience")

 preferences {
   section("Device") {
     input "power",
       "capability.contactSensor",
       required: true
   }
 }

 def installed() {
   initialize()
 }

 def updated() {
   initialize()
 }

 def initialize() {
   unsubscribe()
   subscribe(power, "contact", evthandler)
 }

 def evthandler(evt) {
   if(power.currentContact == "closed") {
     log.debug "Power back!"
   } else {
     log.debug "Power outage!"
   }
 }