Turns out #KiCad plugins are rather easy to write and easy to use - just drop a python script in your /scripting/plugins directory and refresh your plugin list. You don't even have to restart KiCad.

You can even call into wxWidgets to give your plugin a UI.

The applications for this are really endless. Here's a simple example, i wanted to add these fields for the RAM chips that are numbered on the PCB silkscreen. You could do that manually, but I figure if this is something I do a lot, this little script might save me time.