Have you heard about forger? It is a digital sculpting app for iOS that is basically ZBrush available anywhere. You can sculpt while you are on the train, waiting in a queue — literally anywhere.
The toolkit features an intuitive multitouch interface, a number of brushes, the ability to import/export OBJ files, and lots of other amazing features. It is capable of concept sculpting, multi-resolution sculpting, subdivision rebuilding, masking, partial visibility, topological symmetry scanning, sculpt layers, remeshing, auto-retopo, and more.
You can even paint several texture channels (baseColor/metalness/roughness) per mesh, and multiple layers per texture channel, with masking support and adjustment layers using a regular paintbrush or a projection paintbrush.
Supported stylus are: Apple Pencil, Wacom Creative Stylus and Pogo Connect. Users can save their scenes to the internal scene format, import Alembic files or use the popular OBJ file format to import or export new models or basemeshes.
You can get more details here.