Few tests were delivered using mobile phones a few years ago, but the flexibility and capability of these devices make them valuable tools even for high stakes testing. This paper addresses research done through the PAULEX (2007-2010) and OPENPAU (2012-2014) research projects at the Universidad Politécnica de Valencia and Universidad de Alcalá (Spain) to provide a powerful but low cost delivery system for the foreign language paper of the Spanish College Entrance Examination (henceforth PAU). The first project, PAULEX, intended to create a robust mobile platform for language testing while the second, OPENPAU, examined the specific applications of ubiquitous devices to create more dynamic forms of assessment. This paper focuses on the projects' design, testing theory, and technical evolution including visual ergonomics. The current results demonstrate the technical and didactic feasibility of mobile-based formal assessment that aligns student needs with the kind of inferences that the mobile based language test should provide academic authorities.