Most distributed safety-critical real-time systems designed in the past have been specialized to meet the particular requirements of the application domain to which they were targeted. This approach led to specific, inflexible, dedicated and non-reusable solutions, often based on specialized hardware. This report presents an overview of HADES which provides a set of flexible tools built on top of off-the-shelf hardware, and designed to help in the construction of distributed safety-critical real-time applications. In order for HADES to support the execution of the widest range of applications, we have followed a rigorous methodology based on i) the separation of services dedicated to a specific application domain (scheduling policy) from services providing a range of robustness properties common to a large spectrum of application domains (e.g. task dispatching, fault detection, clock synchronization, monitoring); ii) the provision of a precise cost information induced by all these services in order to increase the accuracy of the application feasibility test.