Nice

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  checkboxes: Ember.computed(function() {
    return Array.from({length: 4}, (x, i) => Ember.Object.create({checked: i >= 2}));
  }),
  checkboxesAsJson: Ember.computed('checkboxes.@each.checked', function() {
    return JSON.stringify(this.get('checkboxes'), null, 2);
  })
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{#each checkboxes as |check|}}
	<div>
    <label>
      <input type="checkbox" checked={{check.checked}}>
      A checkbox
    </label>
  </div>
{{/each}}

<pre>{{checkboxesAsJson}}</pre>

{{outlet}}

<br>
<br>

twiddle.json

{
  "version": "0.11.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.10.2",
    "ember-data": "2.11.0",
    "ember-template-compiler": "2.10.2",
    "ember-testing": "2.10.2"
  },
  "addons": {}
}