This study takes a design-based research approach to explore how applications designed for mobile devices could support reflection in learning in K-12 education. Use of mobile devices is increasing in schools. Most of the educational apps support single-person use of interactive learning materials, simulations and learning games. Apps designed to correspond to collaborative learning paradigms, such as collaborative progressive inquiry or project-based learning, are scarce. In these pedagogical approaches, reflection plays an important role. This paper presents a design-based research study of mobile device apps, ReFlex and TeamUp, that are specifically designed for use in student-centred and collaborative school learning, in which continuous reflection is an important part of the learning process. The design of the apps has relied on earlier research on digital tools for reflection and research about mobile devices in classroom learning. The design of the apps was accomplished as part of the qualitative design-based research conducted with a total of 165 teachers in 13 European countries. As a characteristic for a design-based research, the results of the study are twofold: practical and theoretical. The apps designed, ReFlex and TeamUp, are practical results of the qualitative research carried out in schools with teachers and students to understand the design challenges and opportunities in schools, to renew their pedagogical practices and to take new tools in use. To understand better the capacity of the apps to facilitate reflection, we analysed the apps in light of earlier studies concerning the levels of reflection that digital tools may support and categorisations of affordances that mobile device apps may provide for classroom learning. Our research indicates that there is potential for fostering the practice of reflection in classroom learning through the use of apps for audio-visual recordings.