A quick search on steem tools shows this browser extension that will check for you: https://steemit.com/steemit/@fleuri/steemit-notifications-browser-extension-download-now

I'm going to try it out, but what I would really like is to get mobile notifications so I don't need to be on my computer to see when activity happens. The mobile site is ok, but doesn't really work well to that end.

I'll try out IFTTT, see if I can't somehow make it work. Not sure if I'll have any better luck, but we'll see.