Research on Moving Object Databases (MOD) has resulted in sophisticated query mechanisms for moving objects and regions. Wireless Sensor Networks (WSN) support a wide range of applications that track or monitor moving objects. However, applying the concepts of MOD to WSN is difficult: While MOD tend to require precise object positions, the information acquired in WSN may be incomplete or inaccurate. This may be because of limited detection ranges, node failures or detection mechanisms that only determine if an object is in the vicinity of a node, but not its exact position. In this paper, we study the processing of spatio-temporal queries in WSN. First, we adapt the models used in MOD to WSN while keeping their semantical depth. Second, we propose two approaches for processing such queries in WSN in-network instead of collecting all data at the base station. Our experimental evaluations using simulation as well as a Sun SPOT deployment show that our approaches reduce communication by up to 89\%, compared to collecting all information at the base station.