Designed to visually compliment the default UI for dragonriding, this weakaura shows a simplified estimate of movement speed behind your Vigor. The bar shines blue during Thrill of the Skies buff and also has a speed threshold marker in the middle of the bar.
Since the point of this design was to be pretty, the weakaura only loads once your character has talented the 'Beyond Infinity' 6th Vigor point at the bottom of the dragonriding talents tree.
The flight speed estimates can not work while in dungeons or some zones that do not have co-ordinate data. The very clever calculations and coding for the flight speed was taken from an early dragonriding weakaura (possibly Grey's or Darian's) but I cannot see the original source.