Abstract: A social-mobile-local (SML) system and environment includes user mobile devices, a distributed communications network over which the devices communicate, a means of sensing proximity between pairs of mobile devices, and one or more SML databases and programs resident on the user mobile devices, on remote computers, or both. Challenges addressed include prevention of “alert flooding,” privacy protection, credential verification, entering detailed data on mobile devices, power-saving, and improved quality in both the choice and the content of notifications.