An embodiment of a system comprises one or more processors; and one or more memories adapted to store machine-readable instructions which when executed by the processor(s) cause the system to: receive tracked user device information from a distributed network of sensors configured for tracking user device information associated with one or more user devices of corresponding users in a proximity of the distributed network of sensors, wherein the user device information is tracked even when the corresponding users have not opted in the one or more user devices to be tracked by the distributed network of sensors; store the tracked user device information in a tracking database, wherein the tracked user device information is stored even for corresponding users that have not been identified and is for later use when such corresponding users are identified; and analyze the tracked user device information to infer interests of the corresponding users.