Up until very recently, applications designed for Google Glass faced several key limitations when using the RESTful cloud-based Mirror API. Chief among them, was the requirement for Internet connectivity. Well, Google intends to change this with various new APIs introduced with the Google Glass Development Kit, or GDK for short. These allow offline apps that have real time user responsiveness, apps that work without network access, and apps that can make use of deeper access to hardware features.
The GDK serves as an add-on to the Android SDK that allows you to create applications designed for Google Glass (dubbed Glassware). The GDK can be installed in preview form, directly from the Android SDK install manager. As such, building Glassware involves much of the same procedures as building a standard Android application. However, applications built using the GDK add-on will have access to voice, can create persistent cards, and can detect gestures.
Alongside the GDK preview release, Google also showed off five new apps (Strava, Allthecooks Recipes, Word Lens, GLU, and GolfSight) that make use of the new features in the GDK. These are featured on the MyGlass page.
More information on the GDK can also be found in the GDK Sneak Peek presentation below: