I'm actually working on a product right now that provides that precise functionality (and more!) for Gmail. It also lets you schedule when your email arrives for specific groups or single contacts. It's https://lightermail.com and we'll be opening up the beta in a week or so. Hope it helps
Just to comment on your landing page: Your comment here told me much more about what this is about than the copy there.
Unless you're counting on the incoming links' context to inform people what it's about (if you do, fair enough), I'd suggest a bit more info to the potential users.
