Novel and more pervasive healthcare technologies foster an increase in the expectancy of life in next decades. In this field, distributed and networked wireless embedded systems, such as Wireless Sensor Networks (WSNs), suit well with the requirements of ambient care systems, i.e., continuous monitoring of aged or impaired people for their own safety, without affecting their daily activities. In this paper we focus on the problem of knowing the position of people in their own house, without they need to carry any device. Preliminary results of the implementation over a real WSN testbed show good system performances that meet our expectations.