This, to me, is the winner, minus the bouncing. Email servers or clients can append headers based on what content is in the mail, and that information can be used to provide context sensitive app links. I can imagine a big button next to an email that says "Add to Calendar" or "Send to Evernote" or "View Map/Directions". I think Gmail does a good bit of this, so if they can provide hooks for more external services to capture, it would be a huge win.
Ah, that makes more sense. I don't make appointments over email, so bounce an invitation and they can see me in person. I've always liked the idea of email as a non-guaranteed protocol.
