The explosion in the instrumentation of our environment is driving the need for developing sensor networks that not only observe and measure but that also show a high-level of fault tolerance. Towards this goal, we identify faults and key challenges related to the development and deployment of self-managing dependable sensor networks, on the account of two use cases: a monitoring system and a geo-localization application. We then cater requirements and envisage the design of a fault injector which deliberately injects software faults into an operational sensor network to determine if the target offers an effective response, and hence evaluate the dependability of the network. Taking into account the distributed nature of sensor networks and their inherently unsafe (wireless) communication medium, we then insert in a distributed manner communication-related faults and monitor the network under study in order to detect and diagnose any resulting error.