Using Wordpress attached image "custom URL" outside the content

The new editor in WP3.5 gives the ability to add a "Custom URL" to an image that you can attach to a page or post. The caveat is that this URL is only available when the image is used via post_content.

I wanted to use this feature outside the content's text and hit a wall. My solution is a hack but maybe helpful for others.

<?php
//define the arguments to retrieve the posts attachments
    $args = array(
        'post_type' => 'attachment',
        'numberposts' => -1,
        'post_status' => null,
        'post_parent' => $post->ID
    );

    //get the attached images
    $attachments = get_posts( $args );
    //next, see if a custom url is entered via the "alt text" input field since this registers a post_meta
    for($i=0;$i<count($attachments);$i++){
        $url = get_post_meta($attachments[$i]->ID,'_wp_attachment_image_alt');
        $attachments[$i]->url = $url[0]; //add url to attachment
    }
?>

After that, simply loop through the attachments when needed and echo the 'url' parameter.