During the last couple of years we've collected a lot of data about browsers and devices and use that data to constantly improve the accuracy of WhichBrowser. Some of that data may also be useful for others and because of that we've decided to make it freely available - for anybody to improve other browser detection libraries or however else you would like to use it.
For now the data is limited to mobile devices - phones and tablets - but in the future I plan on releasing more data, including feature support data from html5test.com.