Calculate phone angle (Android)

I know this has been asked before, but I haven't found the answer I am looking for.

All I want to do is hold my phone up at the sky, and know the angle at which I am holding it with respect to the horizon. So if I am holding it directly above me (screen facing ground) then it should read 90 degrees, and if I hold it in front of me (screen facing me), it should read 0 degrees.

I have fumbled through some basics of getting data from the accelerometer and I believe I have the X, Y and Y values from it. How can I take those points and find my angle? Below is my OnSensorChanged event that I gather the coordinate from.

    public void onSensorChanged(SensorEvent event) {
    // TODO Auto-generated method stub
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER)
   mGravity = event.values;
if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD)
   mGeomagnetic = event.values;
if (mGravity != null && mGeomagnetic != null) {
   float R[] = new float[9];
   float I[] = new float[9];

  boolean success = SensorManager.getRotationMatrix(R, I, mGravity, mGeomagnetic);
   if (success) {
       float orientation[] = new float[3];
       SensorManager.getOrientation(R, orientation);
       playerAngle = (float) Math.toDegrees(Math.atan2(orientation[1], orientation[0]));

    }