I'm specifically talking about this one app. No DJ worth his salt is going to forego the control and features available to him at this turntables/mixer/laptop to DJ a show on his watch. The most I can see this being used is in a pinch if the DJ has to step down for a few minutes to handle a situation.
Bingo. All the DJs I know use turntables professionally. That's how it's done. It's good only for a few seconds if the DJ needs to get a drink or rotate with someone. But that's about it.