Not a full solution, but there's the API at https://hnstream.com/ for getting realtime updates of comments, which could be used to build a notification system.

Check out this workflow: https://pipedream.com/@dylburger/google-alerts-for-hacker-ne... . Just follow the instructions in the README, changing your KEYWORDS to the set of keywords you'd like to receive notifications for.

You can run the cron job up to once a minute for free, so it's pretty close to realtime :) .

I use F5bot and it’s great

Seconded. I have watch words setup for several keywords. I turn off lobste.rs since I feel HN is already high enough for me in the ivory tower (aka I haven't networked enough to get an in crowd lobsters invite).

I recall Cloudflare CTO, jgrahamc, mention he uses / built exactly what you ask for [0].

[0] https://news.ycombinator.com/item?id=19486562

"I try to answer questions about Cloudflare, or comments about the company, here when I have the time. I do the same on Twitter (and to a certain extent on Reddit). I have code that monitors HN for mentions of "Cloudflare" and emails me within a couple of minutes."

I'm building a service that lets you subscribe to feeds and optionally apply filters. If you used hnrss with it you could probably achieve your goals?

Hacker News is included in my companies website:

https://lettergram.net

And

https://projectpiglet.com

At one point, I also built a chrome extension with similar news feed functionality for a client through Gigster... (I think it was an Admin for HN). Can’t release that though.

We're not quite real-time but this is in our wheelhouse https://www.civicfeed.com/

What would gain with realtime? Genuine question.