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.