You could add some code to your onSensorChanged()
method. First, check the values to see if they are < -100 and if they are, set the text to whatever you like. If they aren't, then do what you already were doing.
@Override
public void onSensorChanged(SensorEvent event) {
if (event.values[0] < -100 || event.values[1] < -100 || event.values[2] < -100) {
acceleration.setText("You have X, Y, or Z less than -100");
}
else {
acceleration.setText("X: "+event.values[0]+
"\nY:"+event.values[1]+
"\nZ:"+event.values[2]);
}
}