There's also https://github.com/thp/urlwatch/ - (not aware of any SaaS offer - self-hosted it is).

Yep, changedetection.io is a good project. With Site Spy, I wanted to make the browser-first workflow much easier: install the extension, connect it to the dashboard, click the exact part of the page you care about, and then follow changes as diffs, history, or RSS with very little setup. I can definitely see why the open-source / self-hosted route is appealing too.

Sure but this one has a MCP server, costs money, and was presumably made last night!

Looks cool and this can be self hosted and it is for free.

Nice will try this out!