It seems like you simply ping the relevant site to see if it is alive. You could do this for all sites and see which are alive or dead, but that's a lot of work and information. Assuming that people check websites that are not loading for themselves, this allows you to much more efficiently comb the internet for sites that are down. Still, why would you want this information? Also, what benefit do you provide the user that they can't get from their own browser?
It is more than a simple ping, it actually issues a full request according to the given URL scheme.
Sitemeer is not supposed to collect vast uptime information from the entire Internet but only to provide realtime snapshots. This mostly comes in handy when you cannot reach a site but are not sure whether the site is really unavailable or there is merely a routing problem.
