This disclosure describes a distributed reader architecture for a mobile computing device such as cellular telephone handset. One claim recites a portable computing device including: memory for storing a library of processing components, the library including a signal detector component and an audio fingerprinting component; a microphone for capturing ambient audio; one or more processors configured for: invoking the audio fingerprinting component for processing captured audio to produce an audio fingerprint, wherein the audio fingerprinting component comprises a filtering process, in which the filtering process produces components of the captured audio that are used to produce the audio fingerprint; and invoking the signal detector component, in which the signal detector component comprises a fast detect process for analyzing the captured audio to determine the presence of an auxiliary signal within the captured audio, and when the presence of the auxiliary signal is detected, controlling the signal detector component for detecting the auxiliary signal to yield a detected auxiliary signal. The device further includes a communications output for communicating the audio fingerprint and the detected auxiliary signal to a remotely located server. Of course, other claims and combinations are provided as well.