Sony brought a Tennis Sensor to the market, demonstrated at CES in January 2014. The unit attached to a tennis racket and measures among other things the impact speed of the ball and the area where the ball touched the racket. A companion application collects the data and provides useful statistics. The Verge published a review of the unit, that was first introduced in Japan, and shipped eventually in the US and elsewhere.
The San Diego team supported collaboration with Tennis Racket manufacturers, and created applications for the sensor, such as a video digest (i.e. based on the measured data and a video of a full training sequence, a tool would automatically create a collection of just forehand plays for further study).