While I was amused yesterday with the tiny DJ controller hooked up to an iPhone, I love the sight of an iPad at the heart of a professional DJ setup. YouTuber Fernando Midi hooked up his Pioneer Mixer and PHASE timecode control to DJ Player Professional. Because DJ Player Professional lives up to its name, all of this works! There's an additional video documenting all of the connections.
Since Pioneer released Mixers S7 and S11 to be "Class compliant", it was easy for iOS to recognize the part of audio and Midi from these mixers, enabling Midi mapping and audio configuration.