The technology contained in them is unreal. From a safety perspective, they can monitor temperature and other health indicators. They also monitor hundreds of things the person is doing like speed, distance run, etc. They are monitored in real-time by staff, and also studied later. I've seen an article where UGA coaches had someone slow down and take a breather because they were over-extending. Likewise, they've chewed some ass when it's obvious that someone is half-assing it.
Now, the question is why a bra? It holds the technology in the optimum location and also makes sure it is connected to the GPS system into which all the data is constantly loaded.
What does the catapult vest track?
These GPS devices are able to capture over 1250 data points per second to measure how much and how hard the players are working, and players and coaches are able to analyze data such as total distance, top speed, number of sprints, sprint distance, power, load, intensity, and more.
That and boobs.