Wireless sensor networks are an important component of the broad framework of ubiquitous computing and are increasingly deployed in a wide range of applications and scenarios. There are many challenging issues that pertain to sensor data management, typically in the areas of analysing this data and communicating this data. In this paper, we present a novel use of sensor readings/data in wireless sensor networks. We propose and develop a model that controls the operation of the sensor nodes themselves using the data from sensors. This ?context-awareness? of the sensor nodes enables considerable energy savings in sensor networks. We present experimental validation of our model using the tinyOS sensor toolkit.