There will be the eXODA WebsiteWatch. An easy to use iPhone app that allows you to monitor a url for changes.
The app will be available in April 2020.
What makes the app special?
The website requests are handled externally by a server. So the app is not dependent on the goodwill of your IOS. What does that mean? The Apple IOS organizes the allocation of background computing capacity on your iPhone or iPad. Therefore it makes sense in this case to have an external server do the calculation and check for website changes. If you add a URL to your watchlist, it will be visited in regular intervals. The notification is a push message.