This paper presents the use of mobile devices by students of linguistics, future foreign language teachers, outside the university and in-campus, and their vision of the potential usefulness of such devices for language learning at tertiary level. As various characteristics of mobile devices influence their usability, users select a device to fit specific needs. This article discusses student teachers' preferences of the use of mobile devices in the light of boundary objects theory (Star, Griesemer, 1989; Star 2010). Although they use mobile phones mainly for communication and orientation in both contexts, the functionalities are different. For example, they use phone calls outside the university versus sms in-campus, city public-transport website versus weekly schedule. The device turns out to be so flexible that allows for a selective use of its functionality depending on the context.