I came across a link to COMTrace from Scott Hanselman. This tool allows for interception and logging of COM traffic. I just tried it out, and it mostly works on some of my more complex MIDAS applications. Granted, it is far from perfect (e.g. I needed to start a new process multiple times before I could get it to work when tracing an app server, or it would hang when starting a client process), but I was able to eventually use it to get tracing information on all of the round-trips that the application makes, including seeing parameters being passed from client to server. From the history log, it appears that the last change was in 2002, so it's a bit dated.

A while back, I was going to develop a tool like this, and actually had some things working on the Delphi level by intercepting VarDispHandler, but that would only work within an application, and for late-bound calls. That didn't sit well with me, as I wanted all traffic intercepted, be it early-bound or late-bound, and I didn't want to necessarily instrument my applications with my tracing/hooking code. I started looking at Keith Brown's Universal Delegator, and associated tools, and was going to go down that route, but the priority changed on having this tool, so it got shelved. It's nice to see that something is out there, even if it is imperfect.