Soon, the New York Police Department will ask residents how they are doing through apps already installed on their smartphones. An offshoot of the department's CompStat program — a data-driven tool for addressing hot spots for crime — the "sentiment meter" is intended to gauge the areas where police-community relations could be improved. The system will use location technology to send out smartphone ads that contain survey questions along three themes: Do you feel safe in your neighborhood? Do you trust the police? Are you confident in the police department? Responses to the eight-second surveys will be bundled anonymously, and precinct commanders can use real-time measures of public attitudes they receive to change block-by-block deployments or take other steps to address residents' concerns. Policing watchdogs and civil libertarians will be monitoring the rollout.