render() {
  return (
    <View style={{width: '80%', height: 150}}>
    { /* render Modal content */ }
    </View.
  );
}

Navigation.showOverlay({
  component: {
    name: 'example.Overlay',
    options: {
      overlay: {
        interceptTouchOutside: false // this make touch events pass through the invisible parts of the overlay
      }
    }
  }
});