Safety Unit is a security ring linked to a mobile app. The ring is provided with a camera and a button with different ways to be pressed, so a user will be able to: record, call the police or call an ambulance. In addition, it can emit a sound (optional) to warn nearby people that the user is in danger.
The mobile app notifies other users (within a certain perimeter) that an incident has occurred. They can see on a map where the user is and whether someone has already called the police or emergency services. With that information, other users can record or take pictures if they are close enough (these files are sent to a police server and are not stored on the users' phones). They can also call the authorities and report the incident. Furthermore, if they feel safe doing so, they can directly help the user or try to apprehend the perpetrator — since they are connected, they can coordinate to assist.
If you want to know more about the UX/UI process, read my article: Design Thinking: Improving Citizen Security. Part I.