As mentioned by others you need to capture the mouse. Here's a sample based on your code illustrating it:
private void InitializeCursorMonitoring()
{
var point = Mouse.GetPosition(Application.Current.MainWindow);
var timer = new System.Windows.Threading.DispatcherTimer();
timer.Tick += delegate
{
Application.Current.MainWindow.CaptureMouse();
if (point != Mouse.GetPosition(Application.Current.MainWindow))
{
point = Mouse.GetPosition(Application.Current.MainWindow);
Console.WriteLine(String.Format("X:{0} Y:{1}", point.X, point.Y));
}
Application.Current.MainWindow.ReleaseMouseCapture();
};
timer.Interval = new TimeSpan(0, 0, 0, 0, 100);
timer.Start();
}
Capturing the mouse before getting the position to get the position anywhere on the screen and releasing it after to resume normal mouse functionality.