jCheck is a simple service to check for changes in webpages. Add a URL, choose a name for it and the checking interval (20 minutes, 1 hour, 1 day...). And you can take advantage of the advanced mode to set headers, parameters, HTTP method etc. Everything is done on the server, so wherever you are jCheck will alert you (by email or by notifications on your device) whenever anything changes on that page. A snapshot of the page at the time the change was detected is also saved, so you can see how it changed over time and maybe see the last change if the site is down.
On the website, you can also select a specific part of the page to monitor: http://jota.pm/jCheck