Googling a little bit I came to the following solution and it seems to work fine:
- Download Glass Launcher (which has been updated for XE12) and import it in Eclipse as a new project.
- Right click the project you just created and select "android tools" and then "add support Library...". if you skip this step Eclipse will not succeed in converting the source code into dex
- Now install Settings.apk
- Now turning on our Glass and swiping left you'll have the possibility of launching Settings from the Glass Launcher Card.
- Open Settings, tap on bluetooth and start inquiring for nearby devices.
- Select your bluetooth keyboard and follow the on-screen instructions to pair it.