This should also work in functions.php:
$post_id = $_GET['post'] ? $_GET['post'] : $_POST['post_ID'] ;
$template_file = get_post_meta($post_id,'_wp_page_template',TRUE);
// show meta if post/page uses specific template
switch ($template_file) {
case 'page-full.php':
include 'meta-boxes/meta-pages.php';
break;
default:
// do nothing
}
// show meta if post/page has specific id
switch ($post_id) {
case '84':
include 'meta-boxes/meta-whatever.php';
break;
default:
// do nothing
}