thanks for the reply
so the object i have in mind is to fill a gap in WP where readers can be notified when a page is updated without having to make a new post and this is not possible via RSS (absent a plugin perhaps, but not everyone uses RSS)
i think a simple label, name field, email field and a submit button would be needed that can be auto-inserted globally (all pages) at page top/bottom via an option or manually via shortcode
in the editor, a checkbox could be added which could be used to manually insert the form, or override insertion if the auto-insert option in settings is enabled
the only purpose for the name field would be so that a {name} variable could be used in the email template to personalize the mail
CSS could be external provided classes/id’s are added
something would need to be done so that a minor page update (fixing a typo) doesn’t trigger mails – perhaps this might require a second checkbox in the editor (‘notify subscribers’ or whatever)