It would depend on how you structure your inbox for the most effective/efficient approach. I personally use the "Inbox Zero" approach and try to keep my inbox empty. This means having a ton of folders/labels. If you are familiar with "Getting Things Done" (David Allen), all email can be broken down into 3 categories: 1) I need to take action on it; 2) save as reference; 3) not actionable, not reference material == garbage.
So before writing a script to handle your situation, do you read emails and know you have to reply later? If so, create a label for that purpose (like "Needs Reply") or something. Then the script can just check that folder, and/or your the Inbox for any unread emails less than say 2 weeks old.