In this paper we present an active tag emulation system that is used to carry out live experiments with active tag applications. Its two main components are the wireless communication emulator QOMET, and an active tag processor emulator. Experiments are performed using the experiment-support software RUNE on StarBED, the large-scale network testbed at the Hokuriku Research Center of the National Institute of Information and Communications Technology, in Ishikawa, Japan. We illustrate the use of our emulation system with a detailed study of a pedestrian localization application. Emulation is used during the development of the pedestrian localization system so as to perform a wide range of experiments easily and in a repeatable manner.