I would like to know if i could launch via a Python GUI an ogr2ogr command :
ogr2ogr -f "GPX" -nlt POINT "C:\....gpx" "C:\....mif"

I would proposate a GUI where people choose in 2 fields their files, select "POINT" in a list (if Waypoints and POPYLINE for Routes or tracks) and clic OK to launch the batch.

Thank you very much for your help.

Yes. That would simply be a system call, which can be achieved by any number of Python methods (popen, os.system, subprocess, etc.).

As far as the GUI portion that can also be achieved by any number of Python GUI toolkits (wxPython, Tkinter, EasyGUI, etc.)

I refer you to google for any more information on those topics.