Some are are custom built from apis but I daresay you can find just about anything to hit a webhook or integrate into slack or elsewhere nowadays. Some examples are https://littlebirdie.io/ I use to filter hackernews, Zapier for RSS & filtering feeds, google calendar etc, nothing complicated, just know what you need from a specific service then figure out a way to get it to yourself in a recurring distraction free manner be it an existing addon or something you can roll yourself.
Not OP, but I think that the idea is that if a notification makes it through the system, it has been filtered to be worthy of distraction. So, there isn't a cognitive cost to the user of "is the notification worth reading" since it has already been determined to be that way.
You're right. On average I probably get about a dozen spaced out during my working hours, 10am to 4pm. On a busy day I might get a couple dozen but the intervals make these easily manageable and I always have priority. If I see something from Gilfoyle in alerts that's probably more pressing than a company I'm following that just released unaudited financials in news. Setup might sound odd but in reality as said above anything that makes it through has some stake in something I'm invested in and want to keep an eye on.
