This is a new development branch of the add-on, support for XenForo 1.1 and below has been dropped completely.
This update will convert the old tables of this add-on to be used with XenForo 1.2. All existing watches will be migrated without data loss. You should perform the update before upgrading the site to XenForo 1.2.
IMPORTANT: If you happen to run into error at the end of the upgrade process because of this add-on, do not panic. Just leave the upgrade tab untouched in your browser, open a new tab (or window) and navigate to http://domain.com/xenforo/admin.php
, login and upgrade the add-on from there. After everything is done, switch back to the upgrade tab and refresh.