These are paintings made thanks to the Brushes application on an iPad.
The artist David Kassan says that he used this same app on iPhone and that it is not quite the same: "This seems to be more about sculpting the painting and it gives the artist more of a feel for the subject matter and composition. The larger screen obviously helps. The options for colour correction and control are far improved from the iPhone."
Maybe he’s right, but I can say that iPhone paintings that I saw are also awesome.