Sadly, no. There certainly are lots of novel keyboards out there that can be googled up, but perhaps the kinds of features that would make a vim/modal-type keyboard be interesting and useful on mobile require further API hooks into the standard text-input controls (to be able to do things like find word and line boundaries, perform complex selections and replacements, etc).

I wonder if ultimately, the advantages of a "stay on the home row" philosophy like vim has just don't really manifest when there's no longer a physical keyboard as the underlying HMI. But the core idea of doing something modal and separating movement/selection from input does still feel valuable.