@Jase_MK
Sorry, but you misunderstand the whole point of a Kalman filter or similar. The whole point of a Kalman filter or similar is to filter out any noise i.e. acceleration from a car etc. So if you tune your filter properly it will filter out all the noise from the accelerometer! To get the total amount of g-force, you just have to calculate the length of the force vector, as I did in the code.
Regards
Lauszus