This book constitutes the thoroughly refereed post-conference proceedings of the Third International ICST Conference on Sensor Systems and Software, S-Cube 2012, held in Lisbon, Portugal in June 2012. The 12 revised full papers presented were carefully reviewed and selected from over 18 submissions and four invited talks and cover a wide range of topics including middleware, frameworks, learning from sensor data streams, stock management, e-health, and Web Of Things.