(PSD) A package for source code debugging of R4RS-compliant Scheme under GNU Emacs by Kellom ?ki Pertti <pk@cs.tut.fi>. Version 1.1. Distributed under GNU GPL. It works with scm, Elk and Scheme->C.
ftp://ftp.cs.tut.fi/pub/src/languages/schemes/psd.tar.Z.