Accessing the Android Barometer using Xamarin.Android

< ![CDATA[
[Activity (Label = "HelloBarometer", MainLauncher = true)]
public class Activity1 : Activity, ISensorEventListener
{
    TextView mainLabel;  

    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);
        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.Main);
        //Detect the barometer
        var sm = (SensorManager) this.GetSystemService(Context.SensorService);
        var barry = sm.GetDefaultSensor(SensorType.Pressure);
        //Subscribe to it
        sm.RegisterListener(this, barry, SensorDelay.Normal);
        // Get our button from the layout resource,
        // and attach an event to it
        mainLabel = FindViewById<textview>(Resource.Id.myText);
    }

    public void OnAccuracyChanged(Sensor sensor, SensorStatus accuracy)
    {
        Console.WriteLine("Things have changed");
    }

    public void OnSensorChanged(SensorEvent pressureEvent)
    {
        Console.WriteLine("Under pressure " + pressureEvent);
        var hPAs = pressureEvent.Values[0];
        var msg = string.Format("Current pressure: {0} hPA!", hPAs);
        mainLabel.Text = msg;
        var calcedAltitude = calculateAltitudeInFeet(hPAs);
        FindViewById<TextView>(Resource.Id.altitudeText).Text = string.Format("Calculated altitude is {0} ft", calcedAltitude);
    }

    double calculateAltitudeInFeet(float hPAs)
    {
        var pstd = 1013.25;
        var altpress =  (1 - Math.Pow((hPAs/pstd), 0.190284)) * 145366.45;
        return altpress;
    } 
}
]]