The notifications are simple, and come to the front of your screen, no matter what app you are in. So long as you are logged into Facebook and Google Chrome is open, you're good to go. You can find the extension by visiting the Chrome Web store.
March 26, 2011
Facebook Notifications from Chrome, Using "What's Up!"
Facebook, the first thing we look for is whether activity has taken place on our wall, or if discussions we've participated in before have attracted new comments from our friends and our friends' friends. It's this Pavlovian need to get feedback and reinforcement for our updates, our shares and our photos, to be part of a continuing conversation. But there's no need to be visiting Facebook.com every couple minutes to see activity. A handy Chrome extension called "What's Up" watches Facebook so you don't have to, pushing notifications in a small window on top of your browser, where you can rejoin the conversation, or simply dismiss.