OCTOBER 8th 2018 — iOS app Concepts just introduced an amazing new Nudge tool, which finally adds a function to a drawing program I have always wished for.
Being vector-based, Concepts already let you always adjust any line and element of a drawing at any point in the process, but the Nudge tool makes drawing with it completely malleable. You can push and pull everything to mold and shape it with infinite freedom.
Incidentally, part of the Concepts team is Finnish. I am not involved with them, though certainly would be proud to be.