Neat article covering a lot of topics, but I'm fairly surprised by these results.

At one point I was looking at building a navigation module for a car using a similar setup to smooth noise, but after some searching I found a paper which showed essentially no benefit from the accelerometer/gyro. The 'drift' on the accelerometer meant it could only filter very fast changes, which the Kalman filter on the GPS board already handled quite well.

I should dig out my little MTK3339 and try to replicate!