Today Google launched the Glass Development Kit (GDK) "Sneak Preview," which will finally allow developers to make real, native apps for Google Glass. While there have previously been extremely limited Glass apps that used the Mirror API, developers now have full access to the hardware.
Google Glass runs a heavily skinned version of Android 4.0.4, so Glass development is very similar to Android development. The GDK is downloaded through the Android SDK Manager, and Glass is just another target device in the Eclipse plugin. Developers have access to the Glass voice recognition within their app as an intent, but it looks like only Google can add "OK, Glass" commands to the main voice menu. Apps can be totally offline and can do all their processing on Glass. They can also support background events and have full access to the camera and other hardware.
Update: Documentation for the GDK has come out, and any developer can add a voice trigger to the "Ok Glass" menu. It's as easy as adding a few XML tags to the strings file. Third party apps are just as accessible as stock apps.
Google showed off a few of the first native Glass apps, and one of the coolest among them was Wordlens, a real-time, augmented-reality translation app. Wordlens works much like it does on the iPhone—foreign-language text targeted by the camera is translated on top of the video feed in real time. This is neat on a smartphone, but on a device like Glass it becomes much more powerful. Just by looking at text and saying "OK, Glass, translate this," the text on the Glass video feed is translated and placed above the original text. Wordlens' app uses the accelerometers to keep the virtual text aligned, all while working completely offline.
Another interesting app that Google showed off was Spellista, a word scramble game that requires use of Glass' head tracking to select each letter. It looks like something straight out of Star Trek TNG's "The Game" episode.
The full GDK walkthrough is embedded above, but don't pay too much attention to the terrible frame rate displayed by Glass. The screen mirroring functionality is extremely slow, but on real hardware, Glass runs the stock apps pretty smoothly. It remains to be seen how much power native apps can actually get out of the system, as Glass only has a 1GHz dual-core OMAP 4430 and 1GB of RAM. Native apps pushing the hardware to the limit or running in the background will make the runtime even worse. And battery life is a problem, too. Even with the extremely conservative stock apps, Glass can only last a few hours.
Google is slowly sending out a new version of Glass to beta testers, but there are no specs published for it yet.
While there is no proper app store yet, the MyGlass companion app is standing in as a temporary distribution platform for Glass apps. Native apps and a real development kit will finally allow Glass to reach its full potential, and by the time the consumer launch comes around, Glass should have a decent ecosystem up and running. Google said that all the demoed apps and the GDK should be out sometime today.