ContextLogger2 (CL2) is a software tool for smartphone data collection, created primarily with research purposes in mind. It can, for instance, be used in user studies for collecting and recording context information such as GPS and GSM cell ID readings, keypress times, application focus changes, etc. The software presently supports Symbian OS based phones, and Android support is under development. CL2 was initially conceived as a small HIIT internal project, and its development continues in contexts such as Google Summer of Code and Helsinki Privacy Experiment.