Viemu looks extremely cool. It adds vi key bindings into Outlook. I haven't downloaded it yet ($79!@?!) but it looks like a full blown text editor and I'm not sure if it allows for navigation. I really would just love to have j, k and / bindings at the inbox level for quickly finding and skimming email messages.
I think this may be the first vi-esque program that I've seen that actually costs money. If anyone tries it I'd love to hear their thoughts.