Package dependencies

There are multiple ways to track the dependencies between objects in an Oracle database, and I won't go into those here.
But what I'd really like (or even need) is a tool that shows the dependencies between procedures and functions within a package body. Not just the simple one-level tree-view you see in all PL/SQL IDE's, but something that shows the package procedure and functions and what functions/procedures (within the packages) they, in their turn, call, as tree nodes:

SOME_PACKAGE

|- PROCEDURE do_general_stuff
   +- PROCEDURE do_this_first
      +- FUNCTION get_that_over_there
      |- PROCEDURE delete_leftovers
|- FUNCTION is_that_so
|- PROCEDURE some_other_things

In fact, this would be such a great help in programming modularly I imagine there should be tools like this already, I just can't find them. So if you have any hints or tips, I'd like to hear them...