monitors your web sites and warns you when any become unreachable (e.g. when a server crashes). Because it checks page content it can even detect when the server is OK, but a site or page is unavailable. There is no limit to the number of sites that can be monitored, including secure sites, and the checking frequency can be anywhere between once a minute and once a day.
SiteUp 2.0 Website - SiteUp 2.0