PagePing is a Chrome extension that auto-refreshes any tab on an interval from every second to every 24 hours, with a live countdown. Give it keywords such as "In stock" or "Appointment available" and it sends a desktop notification the moment that text appears or disappears, then stops refreshing. It pauses while you type in a form, only asks for access to sites you start it on, and needs no account. Free for one tab, with a one-time US$19 Pro for unlimited tabs, an alert chime, random intervals, hard refresh and stop-after-N refreshes.
Refreshing a page by hand to catch a restock or an open appointment slot is tedious, and most monitors are cloud subscriptions. I'm a solo maker in Brisbane, Australia, and built PagePing to do it locally, privately and with a pay-once price.