Android : Get min and max values for getOrientation on accelerometer?

I am currently working with the accelerometer on Android, and have run into an interesting situation. I need to find out the maximum values for the following, WITHOUT requiring the end user to flop their phone around in some elaborate calibration routine. The values I am looking for specifically are...

@Override
public void onSensorChanged(SensorEvent event) {

    SensorManager.getOrientation(outR, xyz);

    float X, Y, XMax, YMax;

    X = xyz[1];
    Y = xyz[2];

    XMax = ???;
    YMax = ???;
}

I've poked around online, but have not had much luck determining what the values would be (it appears it changes from phone to phone), nor seen anyone mention a way to pull that value from somewhere.

Does anyone know how I might determine the maximum/minimum values of xyz[1] and xyz[2]?