In one particular aspect, a portable computing device (e.g., a tablet or smartphone) senses audio and/or image content from a user's environment, and initiates one or more recognition agents (e.g., performing image watermark recognition, image recognition, object recognition, facial recognition, barcode recognition, optical character recognition, audio watermark recognition, speech recognition, speaker recognition, or music recognition). Resource allocation to a recognition agent can be varied based on (a) progress of the recognition agent to achieve its recognition goal, and (b) user interest data indicating user interest in the output of the recognition agent. A second candidate recognition agent can be evaluated for possible launch, based on a relevance score, and a cost score. In some embodiments, the device adapts its operation to changing context, by terminating a first recognition agent in favor of a second recognition agent, without express user instruction to do so. A great number of other features and arrangements are also detailed.