SkateCoach

SkateCoach helps cross country skiers improve their skate skiing technique. The SkateCoach app is run on an iPhone that is carried by the skier (carried in a waist belt or inserted in a jacket and wedged under a waist band).
Here is a video about SkateCoach (cut and paste link): https://www.youtube.com/watch?v=i5dyzSVrcvU

The SkateCoach app records skate motion metrics and scores the quality of the skier's skate technique. After the SkateCoach app is used to record data from a sample session, detailed information about one's skate technique can be reviewed. Types of information that is presented for technique analysis are: weight shift, glide, ski angle, acceleration and velocity metrics.
Until now, coaching of cross country skiing technique has been mostly a subjective activity. "You need to glide more". "Get your arms closer to your body".
There is nothing quantitative about the old school approach to ski technique coaching. A skier does not get feedback as to what percentage difference a technique change makes.
SkateCoach changes all of this. Now a coach and skier can now exactly how technique changes improve glide and speed. SkateCoach can show metrics that are not identifiable by humans. Like what percentage of time is weight shift more on one side than the other. Or what side has slightly longer or shorter glide time, and what the fractional seconds difference is. Or what side has stronger acceleration, and by how much.
SkateCoach, making perfect technique possible.