Between the iPhone (non retina, retina, 3x), iPad (non retina, retina, and pro), and Watch (2 sizes), generating an icon for all those things necessitates no less than 26 images. I have been using a custom Automator script to generate them all through a service that accepts any image as an input, which grew quite big.
As I was updating it, I thought it might be a nice thing to do to let my fellow sufferers have it. So, if that is something you think you might have a use for, feel free to grab it. As a matter of course, it works for me, but I make no promises for your workflow. Just drop me a line if you want to say thanks, make modifications you think might be useful for others, or throw curses at me for having released that just as you finished yours.
It uses no dependancies on libraries or custom applications, by the way.