what is the thing on the back of rugby shirts

The thing on the back of rugby shirts is a GPS tracking device. It is a sophisticated biometric tracking system used by coaches to track a variety of data, such as the players speed, distance covered, and heart rate. The GPS pod is designed to sustain collisions and is cleverly positioned in a sleeve in the back of the rugby jersey. The GPS tracking device is kept in place between the shoulder blades in something called a "Bro," which works in much the same way as a female athlete's sports bra.