In this paper we present a software framework which supports the construction and evaluation of mixedfidelity prototypes for mobile devices. The framework is available for desktop and mobile devices and allows designers and users to 1) test the prototypes on actual devices; 2) gather usage information, both passively and actively supporting contextual and ubiquitous evaluation; 3) convey common prototyping procedures with effective data gathering methods that can be used on ubiquitous scenarios; 4) support in-situ prototyping and participatory design on-the-go. We address the framework's features and its contributions to the evaluation of applications for mobile devices and the field of mobile interaction design, presenting real-life case studies and achieved results. ACM Classification Keywords H.5.2 [Information Interfaces and Presentation (e.g., HCI)]: User Interfaces ? Evaluation/methodology, Prototyping, User-centered design. Keywords Mobile Devices, context, evaluation, eth...