The Open-Xchange Notifier can be installed and updated via the Open-Xchange Updater. This caused the introduction of a new bundle:

com.openexchange.oxnotifier

and its associated package:

open-xchange-oxnotifier.

As both, bundle and package, will be introduced with a 6.22 Patch-Release all necessary changes can be found in git-branch master of the oxupdater-repository.