It's a T-Balancer
It's a controller that let's you monitor temperatures, the flow of a water cooling loop and use that information to make adjustments to the pump and fan speeds
Yes, Linus has one on his personal rig
Even the most elaborated system usually don't require more than 4 channels to be controlled
Don't get disappointed it*s a powerful device that allows for great control
Similar to this device there is also the Aquaero which is also a great device