First version is for scriptlink,
It is necessary to play animation with Alt-a shortcut to get the ipos: http://jmsoler.free.fr/didacticiel/blender/tutor/python_track2ipo_link.htm
The second version uses a popup GUI and replays automaticaly the animation: http://jmsoler.free.fr/didacticiel/blender/tutor/python_track2ipo_popup.htm
These two scripts only works fine with constrain Trackto .
To manage the old trackto : http://jmsoler.free.fr/didacticiel/blender/tutor/python_track2ipo_popup.htm#interface_oldtrackto