I was sitting in the lobby at the local barber shop this weekend and happened to catch a bit of the NFL Scouting Combine where some of the players were wearing this cool shirt from Under Armor called the E39 that had sensors embedded. The shirt has a little green light that flashes on front to give a visual indicator that it is working.
The sensors in the shirt measured statistics about the payer as they ran the 40-yard dash and allowed the teams watching to see what the player's heart rate was and the sensors also measures g-forces. The shirts measurement of acceleration and g-force is something that apparently will help the coaches on the teams and the trainers get the players to optimum efficiency.
According to the NFL.com blog the measurement of g-force can allow the trainers to find things like the player can cut better with his right leg and then allow them to increase training for the left leg for the player can cut as well from both sides. Eventually the shirts will be put into use by other team sports and will trickle down to the public. You can see the shirts in action on this NFL.com video.