Social competency training, as part of psychotherapy, for children and teenagers, requires them to engage on outdoor activities in which they have to complete tasks such as talking to someone or visiting a specific place. Currently, the inability for therapists to monitor their patients, to promote collaborative efforts and to reinforce positive attitudes is a major issue that affects both the therapy process and its results. In this paper we present an evaluation experience of a mobile prototype for a geo-referenced collaborative system that supports in-situ group therapy. The system aims to provide means for therapists to monitor their patients, their locations and achievements and includes communication mechanisms that facilitate cooperation between patients and therapist. We describe the concept behind the project, our initial low-fidelity prototypes and the experiments that were undertaken to validate them. Initial results are discussed and future work is defined.