There are Mac GUI applications which provide a front-end to more geeky commandline tools (often included as a part of the application package). I would like to look at what is happening under the hood of such GUIs.
How to "attach" to an application, monitor it for calls to command line utilities and log a filename and command line parameters of these calls?
A solution can also be an application that logs execution of all applications on Mac OS X (filtering out the most common system calls).
Example GUI frontend: http://xact.sourceforge.net/ (since it is open source one can just debug it, but xACT is just an example. let's pretend we have just a ready-made *.app to monitor).
Update: dtrace can monitor exec calls and print name of the command called. that's a half of the solution, the other half is getting its command line arguments. that's unsolved yet (until someone confirms they have got dtrace to do this).