[Floris]

You can release the product on vBulletin.org, and use it's URL to do the version check.
The version check is done via the admincp > products > dropdown: version check.

You can also host your own version check php file, this is what I use on my server for a particular product (and also makes it vbulletin_audit complaint.

PHP Code:

<?php #config product_version.php (don't include in your vborg .zip release)
$product_version_latest = "1.0"; // change this if you publish a new release on vBulletin.org
#clean = used by wtn_vbulletin_audit.php product made by Floris
#else = what you normaly should get
if ($_REQUEST['do'] == "clean") {
    $product_version = $product_version_latest;
} else {
    $product_version = "<version productid=\"wtn_report_user\">$product_version_latest </version>";
}
echo $product_version;
?>