That's not all that hard. If you look at some of the ones that are all ready created you will find that they will have an option for sending an email. and you can set it up so that it can email you with who won the prize and so on. If you can't find it. Let me know and I'll take a quick look for you. I'm sure that the items that come stock with the shop have 2 or 3 items that send both PM and email.
UPDATE:
I check that file for you and it all ready has that option added for you. When a user buys the item and uses it. It sends you an email. Here look at the code.
EmailAdmin.php
function onUse()
{
global $sourcedir, $item_info;
$to = $item_info[1];
$subject = $item_info[2];
$message = $item_info[4];
// We need sendmail!
require_once($sourcedir . '/Subs-Post.php');
// Hack put in place to allow $_POST and $_GET vars in the $message var
// --Daniel15, 4 Septemeber 2005 2:15PM
foreach ($_POST as $postKey => $postVar)
$message = str_replace('{$_POST["' . $postKey . '"]}', $postVar, $message);
foreach ($_GET as $getKey => $getVar)
$message = str_replace('{$_GET["' . $getKey . '"]}', $getVar, $message);
// Send the email!
sendmail($to, $subject, $message) or die('Error sending message to admin! Please inform the Admin of this error. This item will still be available in your inventory.');
return 'Message sent to admin!';
}