PublicSonar (previously known as Twitcident) is a system for real-time social media monitoring for safety and security, developed in the Netherlands. Customers of the system include law enforcement agencies, municipalities and first responders. The system works by first monitoring local emergency broadcasts for an incident. Once an incident is reported, PublicSonar begins to aggregate relevant social media updates. The service then analyses and filters what it has uncovered. First responders can then use PublicSonar's filters to parse the information that interests them. The system could be used by both first responders and regular citizens to make informed decisions on how to proceed during an emergency. For example, firefighters could be alerted when a second blaze has broken off from the main fire, and direct a team to tackle the new challenge. The service could also be used by people who want to steer clear of trouble in a local area. PublicSonar heavily depends on Artificial Intelligence (AI) techniques, especially Natural Language Processing (NLP).