Its debugging inspection functionality (viewing callstacks) is built on the CLR Debugging Services via ICorDebug, and access through managed code via the low-level managed wrappers from Mdbg (and so I’ve added it to the “Other people’s MDbg work” list on the Mdbg linkfest page). This is like a much fancier version of the Callstack Snapshot tool available.
I think this is a great example of how debugging services can be useful for writing lightweight, specialized, diagnostic tools beyond just super-powerful debuggers. A big part of our motivation in publishing MDbg (and the managed wrappers) was to make these sort of tools easy to write.
The source is fully available, and you can download it and build it with VS. It currently has a bug where you need to either modify the Main() method or launch it outside of the debugger (Ctrl+F5).