functions.php

$highlight_metabox = new WPAlchemy_MetaBox(array
(
 'id' => '_metabox',
 'title' => 'My Custom Custom Meta',
 'types' => array('page'),
 'template' => STYLESHEETPATH . '/custom/metabox.php'
));


function my_admin_scripts() {
 wp_enqueue_style('custom_meta_css', dirname(get_stylesheet_uri()). '/custom/meta.css');
 wp_register_script('meta-upload', dirname(get_stylesheet_uri()).'/js/meta-upload.js', array('jquery','media-uload','thickbox'));
 wp_enqueue_script('meta-upload');
}

function my_admin_styles() {
 wp_enqueue_style('thickbox');
}
if (is_admin()) {
 add_action('admin_print_scripts', 'my_admin_scripts');
 add_action('admin_print_styles', 'my_admin_styles');
}

meta-upload.js

//Adapted from: http://www.webmaster-source.com/2010/01/08/using-the-wordpress-uploader-in-your-plugin-or-theme/

jQuery(function($,undefined){
  // we start by making local references to some global objects so this
  // will compress well. 
  var win=window,
      doc=document,
      current_upload_src,
      original_send_to_editor = window.send_to_editor;

  $(".upload").delegate('input.library', 'click',{}, function(event) {
    var that = $(this), 
    caption = that.attr('title');
    current_upload_src = that.siblings("input.src");
    $("html").addClass("Image");
    tb_show(caption, 'media-upload.php?type=image&TB_iframe=true');
    return false;
  });
  window.send_to_editor = function(html){
    if (!!original_send_to_editor) {
      var fileurl = $('img', html).attr("src");
      current_upload_src.val(fileurl);
      current_upload_src.siblings(".preview").find("img").attr('src', fileurl);
      $("html").removeClass("Image");
      tb_remove();
      current_upload_src = null;
    } else {
      window.original_send_to_editor(html);
    }
  };
});

metabox.php

<label>Mug Shot</label>
<p class="upload">
  <?php $metabox->the_field('mugshot'); ?>
  <input class="src" type="text" size="36" name="<?php $metabox->the_name(); ?>" value="<?php $metabox->the_value(); ?>" />
  <input class="library" type="button" value="Upload Image" title="Upload a mugshot" />
  <span class="preview"><img src='<?php $metabox->the_value(); ?>' style="max-width:300px;max-height:300px"</span>
  <span>Upload an image</span>
</p>