It seems that they are just scraping the data from iTunes. With quick glance they seem to show just that same data which is visible in there. For sure there's some kind of private HTTP API which the clients use to query the data. In addition, appfigures uses your iTunes Connect credentials to get to your private data.
There's an RSS feed http://itunes.apple.com/rss that you can use, but it's slower than straight scraping, which I'd guess many of these sites use.