The project is VirtualMonitor that allows using a computer/tablet/smartphone to be used as a secondary monitor. The rendering is done via either an HTML5 web-browser or a web-browser supporting Java applets -- with the former support, that allows most any modern tablet or phone to work with VirtualMonitor. Right now VirtualMonitor only works on Windows 2000 through Windows 7 but the developer is exploring the process of bringing it into Linux.
In particular, he's started posting in this dri-devel list thread with questions about virtual CRTCs on Linux and virtual DRM graphics drivers. We'll see where this work leads but for those curious about the VirtualMonitor Windows program can visit its GitHub project page.