No apps, but I am the only one I know that has a blank in-box. I use the same time-management techniques that I used to keep my old paper in-box empty. The old 1-2-3 rule.
1 – Delete messages that are just for info or don’t require action – 10% of e-mails
2 – Deal immediately with items that take 5 minutes or less – 80%
3 – File long-term items that require follow-up or require research/in-depth analysis in a To-Do Box – 10%
Percentages may vary, but the technique is pretty sound. The proof is in the in-basket.