Since I keep my browser open 100% of the time, my solution is to enable push notifications in the settings. Since it uses the WebPush API, it works even when I don't have any SN tabs open.
This way works pretty well for me, since then I get a sense of when I have to check SN.
The only reason I'd care for notification via external service would be if I ever get to the point where I have so much interaction on SN that I need it summarized for me.