Action with Json return

If you need to create an action in Magento with content Json as return, you can use this procedure/code :

        $reponse =  new Varien_Object( );       

        ...

        $reponse->setTimeserver( Mage::getModel('core/locale')->storeTimeStamp(   Mage::app()->getStore() ) );

         ... ... ...

        $this->getResponse()->setBody ( $reponse->toJson() );