Body sensor networks (BSNs) have great potential to enable a broad variety of assisted living applications such as health and activity monitoring, and emergency detection. Although several effective application development frameworks already exist for BSNs based on specific sensor platforms (e.g. CodeBlue, SPINE, Titan), effective methods for the platform-independent development of BSN applications are still missing. Such methods would enable rapid development of multi-platform applications and fast application porting from one platform to another. In this paper, we present SPINE2, an evolution of SPINE, which aims at reaching a very high platform independency and raising the level of the used programming abstractions by providing a task-oriented programming model. Furthermore, SPINE2 is exemplified through a case study related to human activity monitoring.