The Mozilla AMO (Mozilla Add-ons) team have update the AMO service to begin listing Add-ons that are hosted on developer web pages rather than on the AMO service. So I created a listing for the Modified Google Notebook Extension, and it is now listed here.
When you visit the Add-on page it will give you all the information about the Add-on but when you click on the link to install the add-on you will be redirected back to this website. You will also be able to rate, review and comment on the add-on there, so please toddle along over there and give it a rating or a review :-) , thanks.
This does not mean that you will be automatically notified when I update the add-on, that is not a service I can offer. However the only time the add-on will be updated is when a new version of Firefox is released. So when you install the new version of Firefox and it reports that the add-on is not compatible with that version, then you'll know to come here or to the add-on page on AMO to download the latest version of the add-on.