I forgot to mention this earlier, but the 8080 emulator can be started in debug mode by passing -D on the command line.  This enters a PDP-10 style DDT.  The DDT family of debuggers originated at MIT and was popular on all DEC machines.  Of course the VT100 didn't come with a debugger in firmware, but the development of an emulator is greatly boosted by having a debugger available to inspect the software being executed.

I'm a bit of a PDP-10 enthusiast, and in particular when it comes to MIT's ITS operating system.  ITS is famous for many things, among those the fact that the user interface is ... DDT!  Since I have been using ITS intensely a couple of years now, I have become very comfortable with DDT.  It's quite a bit like editing text with Emacs (which also comes from ITS), but instead of text you are manipulating memory, instructions, and debug operations.