Force Motion Blur in After Effects does a pretty good job of smoothing out high shutter speed jittery footage and even smooths out a little jello. It just adds motion blur to the parts of the image that are moving so things in the distance or the subject you're tracking are left alone. This GoPro footage is hurting pretty bad. . . Make sure to have your frame blending boxes checked.
Nice that seems to work really well, out of interest what mode are you filming in? 720-50? Thanks for sharing