if you want to track tweetbacks on u.nu (which is the shortest url provider) - add the following code (around #436 - where the other definitions are):
if (!isset($shorturls['unu'])) {
$result = $snoopy->fetch('http://u.nu/unu-api-simple?url=' . urlencode($post->guid));
if ($result && strpos($snoopy->response_code,"200") !== false && $snoopy->results!="" && strpos($snoopy->results,"http://u.nu/") === 0) {
$shorturls['unu'] = trim($snoopy->results);
}
}