Focus windows across Emacs frames

Historically, I've only ever known two great ways of focusing Emacs windows: the built-in other-window command, which cycles through all the available windows, and the ace-window package, offering random window access. It's not that there aren't more or better ways, I just didn't look any further as these were enough for my needs. While I really wanted to make ace-window my default choice, for whatever reason, it never stuck. other-window with a custom M-o binding always felt like the smoother fit for my limited needs. You see, I hardly ever have more than two visible windows, so whenever ace-window kicked into action (for 3 or more windows), it often took me by surprise. The one area other-window didn't fit my needs revolved around focus requiring visual feedback, but I eventually solved that with winpulse (a little package I wrote). As you can see, I'm a simple man using few Emacs windows, and when it comes to frames, I almost never use more than one. That is until somewhat…