Sample plugin for Focus Lab, LLC blog article: http://focuslabllc.com/blog/utilizing-the-template-debugger-in-expressionengine-add-ons

pi.log_me.php

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

$plugin_info = array(
	'pi_name'        => 'Log Me',
	'pi_version'     => '1.0.0',
	'pi_author'      => 'Erik Reagan',
	'pi_author_url'  => 'http://focuslabllc.com',
	'pi_description' => 'Sample template logging',
	'pi_usage'       => ''
);

class Log_me {
	
	public $return_data  = "";
	
	// Support for pre 2.1.3 builds
	public function Log_me() { $this->__construct(); }
	
	
	/**
	 * Constructor
	 * 
	 * Default function when a plugin doesn't have
	 * a third parameter in the tag
	 */
	public function __construct()
	{
		$this->EE =& get_instance();
		$this->_log_item('Log Me: See! This was easy!');
		$this->_log_item('Look, ma! I\'m indented.', 2);
		$this->return_data = 'Done.';
	}
	// End function __construct()
	
	
	
	
	/**
	 * Write items to template debugging log
	 *
	 * @param      string    String to log
	 * @param      int       Tab indention
	 * @access     private
	 * @return     void
	 */
	private function _log_item($string = FALSE, $indent = 1)
	{
		if ($string)
		{
			$tab = str_repeat('&nbsp;', 7 * $indent);
			$this->EE->TMPL->log_item($tab . '- ' . $string);
		}
	}
	// End function _log_item()
	
}
// End class Log_me

/* End of file pi.log_me.php */
/* Location: ./system/expressionengine/third_party/log_me/pi.log_me.php */