How can we encourage people to make sustainable mobility choices, reducing car dependency and the related CO 2 emissions and energy consumption? Taking advantage of the wide availability of smartphone devices, we designed GoEco!, an application (app) exploiting automatic mobility tracking, eco-feedback, social comparison and gamification elements to persuade individuals to change their mode of transport. The app features and contents are grounded in the transtheoretical model for behaviour change and were designed to avoid over-reliance on “one-size-fits-all”, simplistic point-based systems. The GoEco! app was designed in a user centred approach and was field-tested in Switzerland in a three-month experiment involving around 150 voluntary users. In this paper, we present the app’s features and comment on their evaluation from the perspective of the field-testers. The insights we collected through an online questionnaire and individual interviews allowed us to develop recommendations for similar persuasive apps and to identify open challenges for the future. In particular, we recommend to endow such apps with multi-modal travel planning components and features evoking the feeling of belonging to a community, that provide support and helping relationships.