This state-of-the-art paper analyzes the relationship between the OBD-II port of vehicles and smartphones equipped with inertial sensors, with emphasis on the accelerometer, gyroscope, magnetometer, and GNSS reception. Four main directions were examined: vehicle condition monitoring, estimation of fuel consumption and emissions, analysis of driving style and safety, and localization and understanding of the travel context. The synthesis shows that the OBD port provides direct variables from the ECU and the vehicle bus, such as speed, engine speed, engine load, air flow, fault codes, and fuel-consumption-related parameters, while the smartphone complements this perspective by measuring motion dynamics and the space-time context. Combining the two sources enables more robust models for eco-driving, maneuver detection, fatigue assessment, assisted navigation, and distributed diagnostics. However, recent literature highlights persistent issues related to synchronization, variable smartphone positioning, hardware heterogeneity, incomplete access to PIDs, and data privacy limitations. The main conclusion is that OBD-smartphone integration is a low-cost solution with high potential for connected vehicles, but the maturation of applications requires standardization, more robust multi-sensor fusion, and better-labeled public datasets.

Keywords: OBD-II; smartphone; IMU; accelerometer; gyroscope; vehicle diagnostics; sensor fusion