GPS + accelerometer + magnetometer + gyroscope + OLED display, all in a portable enclosure. The idea: a device that knows where it is and can tell you which direction to go.
The STM32L4R9ZIT6 sits at the center, combining multi-sensor acquisition, positioning algorithms, and display control. GPS gives the global position; inertial and magnetic sensors provide orientation in space. The real challenge is in the data fusion layer: filtering raw measurements, compensating for drift, extracting a reliable heading.
The OLED display translates all of that into an interface you can actually use in the field. A nice example of how sensor fusion can be turned into a practical navigation tool that fits in your pocket.