not the tools but the means
I hear tcas, glass cockpits, dme etc. Must not forget that the advancement of most modern avionics is due to advancement in the materials that allowed to take computations made by large mechanical/electrical logic gates to electronics to micro electronics to software. A card file that fits in the nose of a Citation X has more going on in it than avionics racks of early jets that you could about stand up in.
I would also say that the advancement from ADF to VOR/DME/ILS to GPS for radio navigation is the greatest advancement in global systems that have surely contributed to aircraft saftey, by far.