title: Display speed of a unity vuforia tracking target
body: <p>I just finished a Vuforia Unity AR project which successfully tracks a target and moves a unity object. 
  I have done this using AR camera prefab and ImageTrack prefabs.</p>
  
  <p>I have added a 3d sphere with the ImageTrack object. Upon detecting a marker, the sphere is displayed and faithfully follows target where ever it goes.
  I want to display the position or speed of this moving sphere which appears and follows the target. </p>
  
  <p>To start with that I have attached  a gui textbox with sphere with screenoverlay property.
  I set <code>transform.position</code> to this text box and it shows the initial coordinates of ImageTrack when run. As the sphere moves upon marker moving, I want the current position of the sphere to be displayed. </p>
  
  <p>Now it just shows initial position of the ImageTrack even though I placed the code under <code>update(){}</code>
  I need latest current position because I need to calculate velocity, acceleration of this moving sphere.
  Any help plz</p>