New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  isSelectedNone: false,
  
  options: Ember.computed(function() {
    return [
      {
        label: 'First',
        isSelected: true
      },
      {
        label: 'Second',
        isSelected: false
      }
    ]
  }),
  
  actions: {
    setIsSelectedNone() {
      console.log('toggling');
      this.toggleProperty('isSelectedNone'); 
    }
  }
});

helpers.not.js

import Ember from 'ember';

export function not(params/*, hash*/) {
  return !params[0];
}

export default Ember.Helper.helper(not);

templates.application.hbs

<label style="display: block">
  {{input type="checkbox"
          checked=(not isSelectedNone)
          click=(action "setIsSelectedNone")}}
  <strong>
  	Toggle All (isSelectedNone: {{isSelectedNone}})
  </strong>
</label>
<hr>
{{#each options as |option|}}
  <label style="display: block">
    {{input type="checkbox"
            checked=(not option.isSelected)}}
    {{option.label}} (selected: {{option.isSelected}})
  </label>
{{/each}}
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.13.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  },
  "addons": {
    "ember-data": "2.16.3"
  }
}