Every day, First Responders intervene to save our lives. But who ensures the safety of these agents during interventions? The location of first responders is essential to ensure their safety and optimize interventions. Many needs are identified, such as the ability to find endangered officer even without visibility, tracking and monitoring agents in real time and in all environments, identification of secured itinerary, etc. However, today, no commercialized solution meets the requirements of precise and reliable tracking of agents. Nav4you and Jade Tree proposes CHARLI (CHallenging AReas Localisation servIces) project. Our solution exploits an innovative foot-mounted location device merging inertial, magnetic and GNSS raw signals with artificial intelligence and innovative algorithms. Unlike commercially available solutions, CHARLI guarantees 3D sub-meter location accuracy without the need for a ground-based beacon infrastructure. Our device provides necessary elements to localise endangered agents in real time and detect incident regardless of the environment: it works outdoor and indoor. To achieve these performances, we use innovative algorithms to benefit from degraded GNSS data even inside buildings, where it is usually rejected. The temporal difference in magnetic fields makes it possible to obtain orientation information in buildings where a traditional compass does not work. These updates, based on signal analysis, guarantee the desired accuracy in any environment. In addition, a unique artificial intelligence-based model analyzes and detects a wide variety of human movements in real time. This model is used to adapt the algorithms to the environmental and dynamic context. A complete software offer including a supervision software, an optional smartphone user app and a post intervention analysis software complete the solution. The supervision software will allow the unit leader or control team to monitor the position of individual officers in real-time and to be alerted in case of an incident. The smartphone user app will allow the user to benefit from navigation services in some situations and the post-intervention analysis software will allow scenarios to be replayed and interventions to be optimized. Our solution is developed in partnership with professional firefighters in order to meet their specific requirements in the field. Thus, the constraints of cost, size, weight and resistance are integrated into the project. The solution is resistant, lightweight and easy to use. The problem of information transmission in underground or built environment is also addressed, thanks to the use of a low frequency RF communication gateway. However, our solution is also capable of communicating via Bluetooth and Wi-Fi, which allows the use of opportune signals when they are available. Nav4you is a spin-off of Geoloc laboratory from Gustave Eiffel University in France. The Geoloc laboratory, thanks to its involvement in a large number of international research projects, has become an international reference in the field of GNSS and navigation technologies. Nav4you benefits from a great expertise in the field of indoor localisation and cartography. Its innovative device and algorithms have won multiple awards. JADE TREE is a US company specialising in the development and sale of design accessories based on acoustic and thermal innovation. We believe that our CHARLI solution will adapt to the different use cases of first responders and will save lives.