urlwatch is described as 'is intended to help you watch changes in webpages and get notified (via e-mail, in your terminal or through various third party services) of any changes. The change notification will include the URL that has changed and a unified diff of what has changed' and is an app in the OS & Utilities category. There are more than 10 alternatives to urlwatch for a variety of platforms, including Online / Web-based, Windows, Linux, Firefox and Google Chrome. The best alternative is Distill Web Monitor, which is free. Other great apps like urlwatch are Update Scanner (Free, Open Source), Wachete (Freemium), WebSite-Watcher (Paid) and Follow That Page (Freemium).
Distill is a web monitoring tool. It can monitor RSS feeds, a webpage or a part of webpage. Alerts in the form of pop-up, audio or emails can be received. Featured highlights: • Content selection from any webpage including iframes.
Versionista is an online service that alerts you when a Web site changes. It shows you what's been added & removed to any Web page. It records a full page screenshot, and lets you use powerful inclusion/exclusion filters.
Description by owner: "Monitors your website/server for free, 30 seconds interval. Complete delivery test for e-mail servers (sends an e-mail, waits for it to arrive). Alerts via SMS/e-mail. Worldwide network.