Co-drivers in rally cars synchronise information about upcoming turns and obstacles to the total distance travelled. Today, they rely on basic distance measuring instruments that simply counts the number of wheel revolutions. A more advanced system with increased accuracy is desired. Professional race teams utilises data loggers that saves parameters such as vehicle speed and engine RPM. The data provides valuable feedback on driver and car performance. Unfortunately, existing products are too expensive for amateur rally drivers. This thesis describes the design of a combined data logger/trip meter prototype for rally cars. Special attention has been paid to minimise the cost of the final product, by carefully choosing essential but inexpensive sensors, while still providing more than sufficient accuracy. The finished prototype saves information from GPS, gyro, wheel rotation sensors and accelerometers to a memory card. As will be shown, that information is enough for a trip meter with superior accuracy compared to existing products. It is also possible to post process the data to extract interesting information regarding driving skills and car handling.