A portable wireless device includes a processor portion, which is adapted to process audio information in two different ways, for two different purposes. One is to help generate a signal that drives a speaker of the device, so that a user can listen thereto. Another is to process audio information to derive plural-bit data therefrom. The device can then take an action based on the derived plural-bit data. In one particular arrangement, the processor is configured as a steganographic decoder. A variety of other features and arrangements are also detailed, including image-based methods, and arrangements employing various types of fingerprinting.