Focusing images with displays close to the eyes has always been an issue. My advisor, Thad Starner, has been wearing a heads up display that clips onto his glasses for 10+ years. His has the ability to move the image farther or closer so he can set it to appear where his eyes naturally focus.
I believe it's the Micro Optical SV-6. Although the company site seems to be something else. I believe they are now in the business of making those HUDs for ipods (ala MyVu).
