WURFL.io is an incarnation of the original WURFL project hosted on sourceforge.
WURFL (Wireless Universal Resource FiLe) is a community effort focused on mobile device detection. WUFL is a contiunally growing list of all the recognised devices in the world and provides us with valuable insights in to what our clients are using to view our sites.
The idea itself seems foreign when you consider what responsive design is trying to achieve, however it could become valuable for particular use cases that will benefit users. Where ever possible I would encourage you to focus upon device capability detection through Modernizr as this is often the underlying requirement when trying to identify devices.