Methods, apparatuses, computer program products, devices and systems are described that carry out accepting at least one output of at least one of a plurality of user-health test functions, the at least one output at least partly based on an interaction between a user and at least one device-implemented application having an apparent function that is unrelated to user-health testing; and transmitting at least one demographic characteristic of the user based on the at least one output of the at least one of a plurality of user-health test functions.