I haven't used it personally, but Rego Consulting offers an action item "stalker" process that will email people to notify them about overdue items. Perhaps it could be configured to just include deferred items?
regoXchange :: Action Items Overdue Stalker Email - Oracle
All of our action items are generated from processes rather than manually created items, so I'm afraid I don't have firsthand experience with a solution. Our processes examine the responses and send email notifications when appropriate.