The physical safety of vulnerable persons in the public sphere has been an enduring concern since the latter’s emergence, and has intensified with the growth of cities. Indeed the moral value of safety has a special relationship to surveillance, having been the primary justification for the expansion of public area video recording, known as CCTV. Yet the ubiquitization of CCTV in cities across Europe has not eradicated hate crimes, nor other forms of targeting of physically vulnerable people. In recent years this has prompted the rise of ‘safety apps’, applications on smartphones which apply their geo-monitoring, messaging, and other functionalities to allow the user to be surveilled in real time by people that they trust. This postdoctoral project takes place in London, with users who consider themselves physically vulnerable such as women, sexual, gender and ethnic minorities.