In service discovery problem, the mobile actuators send location update messages, whereas the stationary sensors send search messages to learn the latest position of actuators. The task is to minimize the combined update and search message cost, while maximizing the success rate of finding the target actuator, and subsequently to assign a task to it. In the literature, many service discovery algorithms have been proposed for mobile ad hoc networks. As an active subject of research, service discovery in wireless ad hoc networks has been studied for over a decade [4]. The existing solutions can be applied directly to the emerging wireless sensor and mobile actuator networks.