I am currently working on an app that tries to detect different head gestures. I have however noticed in the LogCat the following :
06-11 13:36:32.349: I/RunnableDetector(8406): Recognized gesture with detector: NUDGE Calling listener...
06-11 13:36:32.349: I/GlassSystemServer(8406): Detected head gesture: NUDGE
...
06-11 13:36:41.990: I/HeadGestureManager(8406): Unregistering listener: com.google.android.glass.server.SystemServerHub$4@41bd2328 for head gesture: NUDGE
it seems that Glass can already detect the NUDGE gesture, is there a way to utilize this through GDK?
It isn't documented right now, so probably the feature wasn't ready yet.
So I guess trying: HeadGestureManager hgm = new HeadGestureManager(); didn't give any autocomplete?
If not and you really want to experiment with this (since it looks like it is already there), you could always try using reflection.
A great blogpost on how to use reflection (imo, loads slow but worth it): http://code.tutsplus.com/tutorials/learn-java-for-android-development-reflection-basics--mobile-3203
Edit: also today (June 26th 2014) the preview version of Android L SDK is available, you should probably best download this and check if the new version of Android, maybe has the API's opened.