SMu DoFollow has many DoFollow Options (Manual or Automatism) and included URL Validator (Manual, WP-Cron or Cronjob).
Overview where you can select which Commenter gets DoFollow/NoFollow/Auto
The new admin menu item for the plugin
Configure Options of the Plugin
Optional: Cronjobs can be added for URL Validator
List of all DoFollow Links and URL Validator with multiple Options (revalidate, delete & edit URL and also notify user)