Using custom helpers (components) by CakePHP2.0

AppController.php

<?php

class AppController extends Controller {
	public $helpers = array(
		'Text' => array('className' => 'AppText'),
	);
}

AppTextHelper.php

<?php
App::uses('TextHelper', 'View/Helper');

class AppTextHelper extends TextHelper {
	public function autoLinkUrls($text, $htmlOptions = array()) {
		// override here
	}
}