This add-on allows you to send a reminder to your users and/or user roles when a post, page, or custom post type hasn’t been updated in a certain number of days.
This add-on is useful if you run a site that requires users to update content on a regular basis. For example, if you run an educational institute, you might require that students update their homework or lab notes posts on a daily or weekly basis – with this add-on, reminding them to do that is easy.
Screenshots
Post Update Reminder Notification
Documentation
For more information, I recommend that you look through the full documentation to ensure that this add-on will meet your requirements, prior to purchasing.