Hi, 

ESS has a visual debugger that depends on the availability of source
references. It would be very nice if the debugger could step directly
through org buffers.

ESS was detecting org-src-edit buffers and redirecting references to
original org file for already quite a while. That because of the
availability of org-edit-src-beg-marker in src-edit
buffers. Unfortunately similar functionality is not available in babel.

I attach a patch that would allow ess-eval-buffer from ob-R.el to access
the location of the currently executed block through a temporary stored
marker in org-babel-current-exec-src-block-head.

    Vitalie