SO#45858182

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

controllers.my-route.js

import Ember from 'ember';

export default Ember.Controller.extend({
   myAppFor:"responsive app"
});

router.js

import Ember from 'ember';
import config from './config/environment';

const Router = Ember.Router.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('my-route',{path:'/my-route'});
});

export default Router;

routes.my-route.js

import Ember from 'ember';

function isDesktop(){
 return false; 
}

export default Ember.Route.extend({
  init(){
   	this.set('templateName', isDesktop() ?  'desktop/my-route' :'mobile/my-route'); 
  } 
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

{{link-to 'my-route' 'my-route'}}
{{link-to 'index' 'index'}}

templates.desktop.my-route.hbs

<h1>I am desktop</h1>
<h2>{{myAppFor}} - Desktop</h2>

templates.mobile.my-route.hbs

<h1>I am mobile</h1>
<h2>{{myAppFor}} - Mobile</h2>

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"
  }
}