Tour de France: Greipel wins storm-swept stage to Neeltje Jans

What a stage, what a finish. Flat, cold, wet and windy The final sprints to the finish was so exciting.

I don't know if anyone else is watching, but I was wondering what this thing that is sticking out behind every saddle. They are for GPS,

http://www.cyclingnews.com/news/big-data-comes-to-the-tour-de-france
For the first time in Tour de France history, all riders racing in this year's event have GPS transponders on their bikes, with the live data streaming to Tour organisers thanks to technology group Dimension Data.

Each rider has a transponder mounted to his saddle rails. This will be used by every rider for every stage of the Tour.

The data collected from this will include:

the stage winner’s top speed, average speed and time per kilometre
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