I'm one of the developers behind this project, so I want to jump in because we did explore some of these solutions. You are correct in saying the low frequency

I'm one of the developers behind this project, so I want to jump in because we did explore some of these solutions. You are correct in saying the low frequency acceleration from starts, stops and turns can be distinguished from the higher frequency noise. One big challenge was with orientation. Acceleration can look the same as deceleration and turns from the sensor's perspective, if you turn the phone around. Taking the integral of the gyro reading, the error would grow quadratically, and we found magnetometer readings unreliable depending on the vehicles. Your point about the hunting oscillation is interesting and I agree, estimating the speed would be a great improvement.