The paper discusses the design, implementation and evaluation of a pilot project that integrated inquiry-based learning with mobile game design and introduced mobile devices and sensors into classroom learning. A 5-week classroom inquiry learning project on energy consumption was designed and implemented as a mobile serious game. While engaging in the game and training inquiry skills, students were introduced to basic concepts in the energy domain and to everyday practices of energy consumption in their direct environment. The design was based on a model of inquiry-based science learning with social and open mobile tools developed in the European research project weSPOT. The pilot indicated that using an ubiquitous tool does not necessarily help sustain student motivation. There are indications of gender differences in motivation related to use of mobile devices for learning. These differences should be taken into account in the design of activities. Implementation of the inquiry-based learning model in conjunction with a mobile game scenario into the school practice confirmed the importance of good design with sufficient testing and teacher ownership.