Hi Iain,
Yes, you can do your own calibration within an Android app. Unfortunately we haven’t focused so much on the Android package so far, so there are no graphical examples of how to do this for Android GUI. However, there is a command-line example called MinimalCalibration.cpp included in the Gaze SDK package, that you can use as inspiration.
Note that you also need to set up the active display area for your Android device before calibrating. See the tools folder in the Gaze SDK package for more information.