I can see where this would make the pros laugh. I haven't tried this app. so I can't comment. I regularly listen to my iPad with my good cans.The iPad is certainly capable of good audio.
I can see the potential for something like this. What is an iPad really? or any other tablet? A simple computer minus the monitor and keyboard and has a touch interface. If software can be written for mastering and the hardware is capable of supporting it, how is that different from mastering on a DAW ITB?
We may only be a few computer generations away from this ..or it could be happening now.