I am looking for a Google Chrome extension or Windows 7 program that can trigger a visual, hard-to-miss notification whenever I receive an email from a certain sender (defined by a specific email address) to my Gmail account. Free is better, I don't mind if not open source.
Well, you can tweak the specifics, but I'd use gmail, IFTT and pushbullet to do different parts of this.
You can set IFTT to trigger off an action on a channel on a message from a specific email address on gmail.
I'd use pushbullet's chrome extention or the desktop app to trigger off a notification on your PC though you can pick something else - even some web enabled devices, or even a phonecall in some locations.