Plugin to add text / HTML to bottom of GCE widget

gce-add-text-to-widget.php

<?php
/*
Plugin name: Add text to GCE widget
*/

function gce_after_widget_stuff( $params ) {
	if ( ! is_admin() ) {
		if ( 'Google Calendar Events' == $params[0]['widget_name'] ) {
			$params[0]['after_widget'] = '<a href="http://your-url-here">LINK TEXT</a>' . $params[0]['after_widget'];
		}
	}

	return $params;
}

add_filter( 'dynamic_sidebar_params', 'gce_after_widget_stuff' );