https://stackoverflow.com/questions/44544826/observe-a-change-in-a-boolean-array

controllers.application.js

import Ember from 'ember';
export default Ember.Controller.extend({  
  items:[true,false],
  itemsChanged:Ember.observer('items.[]',function(){
    console.log(' items ',this.get('items'));
  }),
  actions:{
    test(){   
      console.log(' test');
      //this.get('items').addObject(true);
      this.get('items').replace(1,1,[true]);
    }
  }
});

templates.application.hbs

<h1{{action 'test'}}>Welcome to {{appName}}</h1>
{{#each items as |r|}}
{{r}}
{{/each}}
<br>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}