Add Wysiwyg To system config Magento

Adminhtml_System_Config_Editor.php

<?php
/** Create a block adminhtml **/

class Namespace_Module_Block_Adminhtml_System_Config_Editor extends Mage_Adminhtml_Block_System_Config_Form_Field implements Varien_Data_Form_Element_Renderer_Interface
{
    /**
     * Allowed Wysiwyg
     * @return string
     */
    protected function _getElementHtml(Varien_Data_Form_Element_Abstract $element)
    {
        $element->setWysiwyg(true);
        $element->setConfig(Mage::getSingleton('cms/wysiwyg_config')->getConfig());
        return parent::_getElementHtml($element);
    }
    
}

foo.xml

<!-- Add this in any Layout in design/adminhtml -->
<?xml version="1.0" encoding="utf-8" ?>
<layout version="0.1.0">
 <!-- Enabled Wysiyg in system config -->
    <adminhtml_system_config_edit>
        <!-- Called handle Editor to add Js that wysiwyg need -->
        <update handle="editor"/>
        <reference name="head">
            <action method="setCanLoadTinyMce"><load>1</load></action>
       </reference>
    </adminhtml_system_config_edit>
</layout>

system.xml

<config>
  <tabs>
    <namespace_module translate="label" module="namespace_module">
    <label>Tabs Label</label>
    <sort_order>100</sort_order>
    </namespace_module>
  </tabs>
  <section>
    <namespace_module translate="label" module="namespace_module">
      <label>My Custom Label</label>
            <tab>namespace_module</tab>
            <frontend_type>text</frontend_type>
            <sort_order>100</sort_order>
            <show_in_default>1</show_in_default>
            <show_in_website>1</show_in_website>
            <show_in_store>1</show_in_store>
            <groups>
                <namespace_group translate="label" module="namespace_module">
                   <label>Fieldset Label</label>
                      <frontend_type>text</frontend_type>
                      <expanded>1</expanded>
                      <sort_order>10</sort_order>
                      <show_in_default>1</show_in_default>
                      <show_in_website>1</show_in_website>
                      <show_in_store>1</show_in_store>
                      <fields>
                          <fieldname translate="label" module="namespace_module">
                              <label>Field label </label>
                              <frontend_type>editor</frontend_type>
                              <frontend_model>namespace_module/adminhtml_system_config_editor</frontend_model>
                              <sort_order>150</sort_order>
                              <show_in_default>1</show_in_default>
                              <show_in_website>1</show_in_website>
                              <show_in_store>1</show_in_store>
                          </fieldname>
                      </fields>
                  </namespace_group>
              </groups>
    </namespace_module>
  </section>
</config>