How might this tool work in terms of “archiving” a site? This is just something I was wondering given the recent change and controversy about archiving service sites on Wikipedia.

Site Spy keeps snapshot history, so you can revisit older versions of a page and inspect how it changed over time, not just get the latest alert. I’d describe it more as monitoring with retained history than as a dedicated public archive, but deeper archival integrations are definitely something I’ve thought about