As sensors and other pervasive computing technologies are increasingly penetrating ambient assisted living applications researchers, engineers and application architects are starving for tools, techniques and frameworks for building and integrating added-value applications. In this paper we present HERMES, the architecture and implementation of a pervasive computing platform, which supports the development of ambient assisted living applications for the ageing society, with a particular emphasis on memory aids and cognitive training. The platform is integrated in the sense that it enables combined support for memory aid and cognitive training applications. It is also accessible via ergonomic interfaces developed on top of multitouch surface devices. Furthermore, the platform is modular and extensible since it provides Application Programming Interfaces (APIs) for the flexible development of additional applications. Along with the middleware architecture of the platform we also present representative trial deployments, which manifest that the presented platform is an attractive option for building pervasive applications for the ageing society.