What is the small rectangular pad inside the back of rugby tops?

Answer 1

They are the outline of a data recorder that provides coaches stats on your heart rates, distance covered and tackle power, all in real time.

Answer 2

This is a small GPS pack. Its used by the statisticians to see where on teh park the player was, how much running time they had and where to

Answer 3

This is a GPS transmitter. It sends the player stats to the tactical team for post match training analysis