That is a wideband. It's the best and most accurate type of gauge for reading air/fuel ratios, you would use that instead of an air/fuel gauge or EGT gauge. Has nothing to do with the Power FC which would be your actual ecu. The Power FC replaces your stock ecu. The commander allows you to see certain functions while driving and also allows you to tune your power fc. The commander is not necessary, in fact most people just prefer the datalogit.