$view->addHelperPath(
APPLICATION_ROOT . '/library/MyApp/View/Helper/Navigation',
'MyApp_View_Helper_'
);
echo $this->navigation()->myMenu(); // name of your class
From: Getting Zend_Navigation menu to work with jQuery’s Fisheye
EDIT
Sorry I’ve not seen your solution, it is exactly what I’ve posted.
But why this is not a trully extension of menu class?