Health and usage monitoring (HUMS) as a technique for online test, diagnosis or prognosis of structures and systems has evolved as a key technology for future critical systems. The application of HUMS technology requires a portfolio of reliable miniaturized sensors, capable of delivering "intelligence" on the internal and external environment of a system or structure. This paper proposes a fault tolerant sensor architecture and demonstrates the feasibility of realising this architecture through the design of a dual mode humidity/pressure MEMS sensor with an integrated temperature function. The sensor has a simple structure, good linearity and sensitivity, and the potential for implementation of built-in Self-test features. We also propose a re-configurable sensor network based on the multi-functional sensor concept that supports both normal operational and fail safe modes. The architecture has the potential to significantly increase system reliability and supports a reduction in the number of sensors required in future HUMS devices. The technique has potential in a wide range of applications, especially within wireless sensor networks.