The complexity in designing, coding, and testing WSN applications is considered among the most relevant factors that limit the diffusion of WSN technology. In this work we claim that Erlang, a concurrency and distribution-oriented, functional language, could greatly reduce this complexity. Moving from this premise we introduce a new platform, named WSN-Erlang, which leverages the Erlang peculiarities adapting them to the requirements of WSNs. WSN-Erlang also includes a testing and simulation framework, fully supporting the entire life-cycle of WSN applications.