[Too]

There's a lot of focus on his phone. If this guy is really cheating it's probably way more sophisticated than that.

There are super tiny hidden in-ear earbuds that would easily go unnoticed unless someone really looks for it. https://i.ebayimg.com/images/g/E~0AAOSwqABbH4mT/s-l640.jpg Or vibrating devices hidden anywhere else on the body. This paired with some information from the RFID stream, either through some insider or by hacking the Wifi.

As you say there are also lots of other items brought in and worn by the players, looking at the video i see people wearing hats, shades, bags and bulky clothes where you could easily hide all kinds of equipment.