I have a few pages that require login, so all controllers that link to these pages start with
$this->checkSession();
//...rest of the code
I had a similar problem. Where I wanted to stop the user to due to no login. But I wanted to offer a list of links for them not simply redirect them to a login page. I am using CI version 1.7.2 and the $this->_output() $this->display->_output() and $this->output->_display() solutions did not work for me. I was however to get my results using the $this->output->get_output() function.
$this->load->vars($data);
$this->load->view('template');
die($this->output->get_output());