Huginn

Huginn runs "agents" that watch websites, RSS feeds and APIs, then react: scrape a page, detect a change, chain events through other agents, and end with an email or webhook. It has been quietly doing this since long before the current automation wave.

It is a Rails application with an old-school UI, and building agent chains takes more patience than modern visual editors. In exchange, the scraping and event-plumbing capabilities remain among the most flexible anywhere.

For patient tinkerers who want the web watched on their schedule, not a SaaS quota.