The leatest entry into the athlete tracking product arena tracks hits to a sports helmet.
Impakt Protective's Shockbox is a helmet g-force sensor that measures the impact a player sustains and gauges whether a medical assessment is in order.
The device can fit into any helmet with space amid the interior padding so that it's right up against the hard shell. It can be used in football, hockey, lacrosse, and snow sports like skiing and snowboarding.
The sensor, about the size and shape of a wristwatch, goes inside the helmet, against the shell. Depending on the force of the hit is sends an orange or red signal to a bluetooth receiver, a cell phone with a free app to interpret the codes. Ideally, the coach holds the phone, which can track up to 128 sensors at one time.
Internet sources inform me Bluetooth was designed to work in a 10 meter radius, but can carry up to 100 meters. In some sports it seems the data can be delivered in "real time" while in others it'd be downloaded after a game or ski run. I wonder if adding info on where the hit occured and /or the player who made the hit would be valuable.
Other devices of this type have not yet grown to widespread use.