Comment by nicbou
I was thinking of that exact strategy for two scraping problems I have. It would be a good way to gently scrape Berlin.de for appointments, and Immobilienscout24 for new flats.
From what I can tell, it would work fine so long as the user is actively looking at those pages.
Yeah, something generic to work for any use case would be nice, but privacy becomes more difficult as you need to tailor the situation to each site to maintain privacy (i.e. only pull the information on the apartment/flat listing, or public tweet or reddit comment, etc...)