var app = angular.module('plunker', ['ngPostMessage']);

app.controller('MainCtrl', function($scope) {
  $scope.messages = [];
  $scope.$root.$on('$messageIncoming', function (event, data){
    $scope.messages.push(angular.fromJson(data));
  });
  $scope.sendMessage = function (){
    $scope.$emit(
      '$messageOutgoing',
      angular.toJson({"response":"hi"})
    );
  };
});
<!DOCTYPE html>
<html ng-app="plunker">

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="angular.js@1.2.x" src="https://code.angularjs.org/1.2.20/angular.js" data-semver="1.2.20"></script>
    <script src="https://rawgit.com/kylewelsby/angular-post-message/master/dist/angular-post-message.js"></script>
    <script src="app.js"></script>
  </head>

  <body ng-controller="MainCtrl">
    <p>messages should be received every second</p>
    <iframe src="https://rawgit.com/kylewelsby/585b3a5395c6731acc50/raw/f661e856adbccf39549ed7c550661f09158f8d55/index.html"></iframe>
    <br>
    <p>send response after inital message received from child frame.</p>
    <button ng-click="sendMessage();">Send response</button><br/>
    <ol>
      <li ng-repeat="message in messages">{{message}}</li>
    </ol>
  </body>

</html>
/* Put your css in here */