Brother’s Airscouter, Epson Moverio BT-100, getting closer …
In light of all the talk of Google's project glass, there are a bunch of folks suggesting that the other displays on the market can already do what Project Glass is trying to do. And, I will agree, some of these displays are getting closer.
Brother's Airscouter (apparently due out this summer in Japan) is indeed a see-through virtual retinal display, and is "relatively small".
{% youtubes 5rtxz1P2Ogw %}
But, it's a LOT bigger and bulkier, and it's "just the display." No camera. No computer. No sensors. So, in practice, it would be much bigger, and a lot uglier. As a researcher, of course, I'm totally fine with this, since it will let us do the research we want with the platforms we want (from desktop to laptop to tablet to handheld) and not be bound to a specific OS or set of sensors. But, for practical use, that's a huge problem. So, we'll likely be buying some (there's nothing else quite like it coming out), just as we'll be buying other displays!
Epson has an actual see-through display on the market, and it's relatively cheap!
Like Project Glass, the Moverio BT-100 includes an Android device and is see-though. But, it's also stereo! Unfortunately, it doesn't include sensors on the display (either a camera or orientation sensors to tell which direction the head is looking), so it can't really be used for augmented reality. I am not even sure if it includes GPS (to let it at least be used for a limited collection of location aware applications, like Project Glass does). So, again, this isn't really useful for the kinds of things we want to do in AR or even wearable computing. The integration and reliance on an Android device (running a relatively old version of Android) is also a huge problem for folks like me, who want to try new things. We are porting our AR-enabled web browser (Argon) to Android right now, but will only support ICS (Android 4.0) and above; in fact, since there are bugs in the Android webview that won't be fixed till at least the next version (I hope) we probably can't even support 4.0. Having to use 2.2 or other old revs of Android isn't that useful.
So, the world keeps moving forward, things keep getting better ... but we aren't quite there yet!