new topic: quick and dirty rpm related tools

Anyone know of a prewritten script or something that can help me keep
track of extraneous rpms, that I can remove without running into
dependancies.  Basically I'd like to keep up with a list of installed
rpm's that aren't needed by other packages currently installed.  With a
list like this I could find orphaned packages that I no longer need and
can safely remove without running into dependancy problems.  I guess its
sort of like an rpm pruning tool.

Now I don't know if this feature should be rolled into grab...but having
a quick and dirty tool to keep my from collecting cruft on my system.

I could probably bang together a little shell script to do it using rpm
-q statements, but I was wondering if something had already been
written.