The pressure switch in your spa controls the water pressure in your spa. The pressure switch harness is a replacement part for the original pressure switch harness that allows the pressure switch to be connected to the controls of your spa.
The Standard Fusion Docking Station is a waterproof enclosed case that allows you to connect and play your mp3 player/phone from inside your hot tub. From the top-of-the manufacturer of spa entertainment components, Aquatic AV.