This paper reports about the development of a system supporting problem-based learning in the classroom. its Principal design principles are the combination of computer mediated and face-to-face interaction and mobility to ensure a high level of motivation. The main contributions of this solution are: a) being a full peer-to-peer application it can be used in any situation, inside the classroom, in labs, museum or even in the open air, b) the teacher can create new problems "on the fly" and send them to the students anytime; and c) provides the teacher with powerful assessment and feedback possibilities The paper also reports about a first evaluation of the system called MCI-Supporter.