An audience measurement or personalized recommendation system may be actively trained for each panel member for a training period, during which the presence of each member is recorded while content is displayed. Panel members may carry or wear portable devices with wireless transmitters which may be detected by the measurement system. For example, each panel member may wear a wristband including a wireless transmitter broadcasting an identification code, and a measurement device may include a wireless receiver to receive broadcast identification codes and determine that the corresponding one or more panel members are present during display of content. An inference engine may create personalized profiles of each panel participant during the training period. After the training period, panel participants may stop carrying or wearing the devices, and the inference engine may determine, based on the profiles, which participants are likely present when content is being viewed.