The just released "Augmented Reality Eyes" application as far as I know it is the only implemetation so far on any Smartphone platform for gaze tracking with OpenCV on this level.
It was quite a job to implemented (Java / C++ wrappers & libraries for OpenCV and such, you can all well imagine). Indeed any support for using OpenCv in Android is still lacking so we basically did it all ourselves.
You'll see on the related Youtube video that it work at about 10Hz, which is quite good considering how heavy OpenCv is and that GPU acceleration is not useful for these gaze tracking algorithms.
I should add that it is a spinoff of a cutting edge automotive gaze tracking of ours, so proven technology. But the migration to Smartphones is very hard indeed, still. I think only the surface has been scratched of what is possible with computer vision on Android.
We are now working on OpenCV optimization instead of having it all on the Smartphone and so soon the app should work at 20Hz.
I hope to hear from others what their experience has been with OpenCv for Android.