There seems to be a fair amount of buzz, on Twitter at least, around the idea of Sketch for iPad. Sketch has already taken a position on this. The app ProtoSketch seemed to be the closest thing to this so far.
A new app called Pattern was released today. Whether or not it will become an alternative or companion to Sketch, it certainly looks like it could be a useful tool for UX/design concept-work and more.
Pattern is an iPad app with Apple Pencil support that allows user to “Create beautiful, precise, design drawings – Pattern is a simple, focused, drawing application for early stage design and ideation. It focuses on simple design tools rather than fancy brushes and effects. By using gestures to draw, create shapes, and erase, Pattern allows you to spend more time drawing, and less time switching between modes…”