One arrangement concerns a portable device (e.g., a smartphone) that executes plural recognition agents, such as agents that perform fingerprint-based object recognition, fingerprint-based audio recognition, barcode reading, watermark decoding, etc. Each of the agents reads from and writes to a blackboard data structure, to which camera and microphone sensors also post their data. Queues of stored sensor data are thus available for the agents to process. In some arrangements, the agents also post—to the blackboard—estimates of the resource costs required to perform certain functions, and estimates of the quality of results that may be achieved by such functions. This allows the system to make informed decisions about how to deploy the device's limited resources (battery, processing cycles, network bandwidth, etc.). A great variety of other features and arrangements are also detailed.