What is this device on all the Tour de France riders' bikes? What is the device behind the saddle on all the riders' bikes in the 2015 tour? I'm seeing it on almost every bike. It looks standardized and electronic.
This is a special device that gathers the following data, according to this article:


  
  the stage winner’s top speed, average speed and time per kilometer
  the fastest riders up key climbs
  the speed of the winner at the finish line
  the top speed achieved by a rider on the day
  average speed across all riders