Methods, computer program products, and systems are presented. The method computer program products, and systems can include, for instance: recording position data for a mobile device over time, the position data being associated to an identifier of the mobile device; outputting to a user an identification code associated to the identifier; receiving input data from a user, the input data including the identification code and user identifying information from a user; responsively to the receiving the input data from a user associating the identification code and the user identifying information; based on the associating processing the position data and user profile data associated to the user identifying information; sending a message to the user based on a result of the processing.