In one of my previous posts you could read how to make Glassware with the GDK. Glassware that has been made with the GDK can be run offline on the Google Glass and is actually installed on the device itself. It also gives you the flexibility to use the device’s sensors and camera, but in the end it takes a lot of time to build something.
If there is no need to use the application offline, or use the sensors and camera, you could consider using the Mirror API. A concrete example for this could be pushing Tweets from Twitter to the Google Glass.
The Mirror API makes it possible to build web-based services that can communicate with the Google Glass. This functionality is provided by a cloud-based API and does not require code running on the Google Glass.
Here you can find a good article about Mirror API. In this article you can read what the Mirror API does and how to make an application yourself!
Source: http://www.toptal.com/google-glass/mirror-api-google-glass-for-web-developers
Command line Mike 