A portable device is used to capture, in real time, data sufficient to identify a product or service promoted, or a music track played, on a broadcast medium such as radio. The device determines a current frequency setting of a nearby radio by short-range broadcast of a brief audio-frequency signature so as to form a feedback path from the radio sufficient to determine the frequency or station currently playing. The captured data is communicated to a services server to enable quick and convenient purchase of the desired product or service.