I4U has a few details on an impressively lightweight LCD screen from Scalar Corp. that can be mounted on ordinary glasses that weighes a scant seven grams. The screen offers a simulated 14-inch screen with 180,000 pixels (roughly television resolution). It’s not terribly expensive, either, at just $460 or so.
I don’t have a subscription to Nikkei.net, though, so I have no idea what sort of interface it uses. Much smaller than this, though, and it’ll be directly integrated into glasses themselves and we might actually start wearing stuff like this.