Subscriber entity

Provides entity for subscribers who need not be users. For example with phone numbers (eg. Drupal VoIP, SMS Framework), or e-mails, who are not users of the site (no login, username, password, or in the case of phone numbers valid e-mail address). Allows a field, or output of tokens, from the entity to be defined as unique.

The unique field can be used to load the entity. So the subscriber need not know about another ID except the value of the field or whatever.

The entity is fieldable so details of subscription can be added via which ever desired fields: taxonomy topics, entity reference to something else in the site and so forth. Different bundles can be created for different forms of subscription.

Allows for revisions. Thus a subscriber can update their subscription, the changes saved as a new, but not yet the active revision. Changes can then be confirmed via SMS/e-mail. Mechanisms for the actual confirmation are not in the entity - depends on what you are doing.

Caveat: Permissions to access or edit an entity may presently lead to information disclosure - if at the minimum that the subscription exists - configure wisely.

Depends on, and is also exportable via, Entity API.