The company invented a product that can monitor vulnerable people. It is important that they know exactly where their products are located. If a situation occurred where a vulnerable person needs immediate help, first responders can use the knowledge of the location to get to the patient as fast as possible. This thesis investigates if a modular localization solution can be designed for this product. The product will always be located in an indoor environment, which is a difficult place to establish the location. A modular solution is interpreted as a system that has parts that are replaceable. Some parts can be switched out for different parts with the same functionality, with the system still working properly. In order to design this system according to the requirements, the design process was divided in hardware and software. Both were designed in a modular way, yet eventually implemented in one specific way. This was done to get a tangible prototype that could be evaluated and tested. Improvements to the system were also designed, however could not be implemented in time. Nonetheless, the resulting system works well under conditions of intended use. There were some conditions in which the system performed less than required, however this should be fixed once the improvements are implemented. The results indicate that the localization system that is needed for the company's product is possible to be implemented. The next step is to research whether parts of the modular system can be replaced by an improvement. Then the system can be tested in more distinct working conditions, which could not be done during this project. If the system passes these tests, it is ready to be integrated with the other subsystems of the product, such that the company can bring their product to the market.