Just stumbled over this… and I´m soo soo very happy to see this being made! Thank you miyagix very much for your work!! 
It´s one of my top two wished for features in Blenders sculpt mode besides what Wakka proposed in post #14. (some sort of more precise transfer gizmo/option in Sculpt mode). And it is already becoming reality… wha!! Nice!
I test your branch the other and made some quick notes and a short time lapse:
Topograb is almost like grab brush but the difference is when you are really close to the mesh and the speed vertices are moved.
Sometimes the cursor is not take into consideration as the base of the brush in dyntopo and when symmetry is on.
Sometimes symmetry doesn’t work.
In dyntopo topograb brush got crazy after adding more details dyntopo.
is depth missing with topograp?
Working with 2 meshes in 1 object, topograb brush always ignore the mesh on top and when zooming out the brush got confused.
No crash 
That was my feedback, keep up good work
if is too fast just reduce speed.
Hi great work so far, though I am unsure – did this project get discontinued? I can’t find your latest report 
I didn’t know that just now reading meetings and i followed the link, i find out he was dropped out :(, hopefully if he continues on his spare time it will be great.