The present article describes basic ideas of implementation of mobile application dedicated to indoor navigation. Indoor navigation is a complex issue, especially when it comes to large buildings with lots of rooms and rich infrastructure. The goal of the research was to achieve high accuracy and performance of mobile device positioning and indoor routes calculation. Bluetooth beacons were suggested to determine mobile device location. Analyzing the received signal strength indicator (RSSI) and beacons position on the map provided an ability to calculate the distance from each beacon to the mobile device. Trilateration algorithms were composed with Kalman filter which allowed for fast and precise device positioning. To calculate pedestrian-friendly indoor routes the authors addressed game development methods: room map was suggested to be in a form of a polygon with holes, which was decomposed via triangulation and tessellation algorithms. Among all triangulation algorithms that work with "holed" polygons the modification of Earcut triangulation algorithm was considered to be one of the most suitable and efficient. As a result, getting a polygonal mesh of high density allowed to use this mesh as a graph and apply any path searching algorithm to calculate the determined route. The result of the whole research was a working prototype of a mobile application which satisfied performance and accuracy requirements. Preferred algorithms have good potential and can be used as a basis for future improvements. Inaccuracy of measurements should always be considered and its handling is a self-sufficient problem.