Surveillance is an important task for guaranteeing the security of individuals. Being able to intelligently monitor the activity in given spaces is essential to achieve such surveillance. Sentient spaces based on a large set of sensors provide the potential for such intelligent monitoring. However, heavily instrumenting a space with sensors it is not enough to build a sentient space. One needs a software architecture that allows programming all these sensors in a transparent and efficient manner. In this paper, we present SATware, a stream acquisition and transformation middleware we are developing to analyze, query, and transform multimodal sensor data streams to facilitate flexible development of sentient environments. SATware provides a powerful application development environment in which users (i.e., application builders) can focus on the specifics of the application without having to deal with the technical peculiarities of accessing a large number of diverse sensors via different protocols.