Thanks!
What I'm trying to do won't be perfect, but it's still better than doing it all manually.
I created "CallOuts" in 3D environment and I inserted them in a latlong sidebyside 3D VR180 video.
For the Z axis, I tried to create a deepthmap and get a Z value from a DispatityToZ node. It gives me something, but it's not precise enough (in the shot, if the object gets a bit brighter or darker, it fails). So, I just calculate my z value manually comparing the disparity of my 3D callout, once rendered into my sbs scene, with the disparity of the object I'm tracking.
But then, for the X and Y values, I would like to use tracker values, and multiply them to get as close as possible to the correct values (at least when I'm staying not too far from the center of the screen, because on the sides of the latlong, the image deformation will be hard to manage).
... I hope my explaination is not too confused
Anyway, I've just been using fusion for a few weeks, but being able too use 3D callouts and other 3D objects/effects in a 3DVR environment is pretty cool. If I can track objects, even approximately, it would be perfect.