Garmin-Slipstream also uses its Edge 705 computers to display and record wattage information from its Powertap rear hubs but unbeknownst to many, each power meter is also sending data to an innocuous looking little yellow box either mounted beneath the saddle or on the back of the rider's helmet. They're not just storing the data for later analysis though... the Edge 705 already does that on its own.
Instead, it's apparently some sort of real-time telemetry system that transmits each rider's wattage information back to the team cars. Exactly how that information is used during a stage, however, isn't exactly clear. Quite understandably, Garmin-Slipstream officials haven't been terribly eager to discuss the system's details with us.