This document discusses sensor fusion between a car and smartphone to enable new applications. It describes relevant sensors on each device - cars provide power, position and built-in sensors while phones contribute GPS, accelerometer, gyroscope and compass. Obtaining car data via OBDII is described, along with challenges like magnetic interference. Two use cases are proposed: dead reckoning navigation without GPS by combining car speed and phone direction, and vibration analysis using the phone's accelerometer to detect road conditions when driving. Overall, integrating car and phone sensors can provide richer data but also requires handling sensor limitations.