I whipped together a system that can (indirectly) send notifications based on what aircraft are visibile to dump1090 and thought it might be useful to others.
It simply polls dump1090 for aircraft information, filters the aircraft, and then calls a webhook with the information if any planes match a filter. So in my case, I filter on a couple of callsigns I’m interested in, and get a notification if any show up. But you could do basically anything that can be triggered by a GET or POST to a URL - IFTTT springs to mind (although I think they changed to a premium model a while back?).
The code is open source and available on Github. Happy to add example configurations/fix any ‘quirks’ that anyone comes across