Adding Theme Switcher to a Menubar

I have a blog with many themes and I wish to add a theme switcher without editing each theme, also I do not wish to use the meta hook method of adding it, I want to add it into a bar above the blog.

If you look at a site like engadget.com, they have a bar running across the top of their screen & I want something similar for my theme switcher.

Could someone advise which hook I should use to output this information to the browser before WP creates the page? So far I have got something like working with the footer hook and the theme switcher I found here: http://dev.wp-plugins.org/wiki/ThemeSwitcher

<?php
/*
Plugin Name: Switcher
Plugin URI: http://Themey.com/
Description: meh
Author: Simon Pilkington
Version: 0.001
Author URI: http://pilkster.com
*/
function switcher_wp_footer()
{
echo '<div style="border: medium none ; margin: 0pt 0pt 0pt -163px; padding: 0pt; overflow: visible; position: absolute; left: 100%; top: 0px; height: 10px; width: 50px; z-index: 1000000000; float: none">';
echo wp_theme_switcher('dropdown');
echo '</div>';
}
add_action('wp_footer', 'switcher_wp_footer');
?>

As you can see at http://themey.com

Thanks in advance 🙂