The recent updates of the iPhone/iPad app “forger” have an astonishing resemblance to the basic ZBrush workflow with masking, a subdivision level slider, remeshing, brush falloff curves, modifier buttons for invert action and smooth, myriad brushes including inflate, pinch, flatten and polish (“scrape”). The app has been mentioned a couple times before in this forum back when it was a buggy toy.
https://itunes.apple.com/us/movie/the-forger/id514795565