The constantly growing complexity of heterogeneous systems requires effective methods for supporting the designer both during the development of the application and the implementation of the architecture. Unfortunately, existing tools still require that the designer develops large parts by hand, especially when hardware accelerators and partial dynamic reconfiguration are taken into account. This paper presents A2B, an ongoing project at Politecnico di Milano, about a semi-automatic framework to assist the designer during the development of heterogeneous and reconfigurable applications for both embedded and high-performance systems. It allows to start from a C-based description of the behavioral specification to be implemented and to perform a progressive refinement of both the designed application and the hardware architecture. It offers the possibility to specify decisions either by an interactive environment or by automatic algorithms, hiding most of the implementation details to the designer.