This paper discusses the use of off-the-shelf Radio Frequency Identification (RFID) detection as complementary technology to the localization of people (detection and localization relative to the robot) in social robotics scenarios. A novel model for the detection of passive RFID tags is proposed, involving the estimation in real time of a measure of the probability of the tag being detected. The method estimates the location of the tag relative to the reader with an accuracy suitable for a wide range of human-robot interactions and social robotics applications.