I would say the efforts to adapt the frequency response (and thus also partially the localisation) to the individual ear and HRTFs by either mic or optical measurements.
That made me think... To the former group belongs the popular
Smyth Realiser, right? It seems to work wonders for all I could read or hear about them. Another product which is based on mic measurements is the DIY software
Impulcifer, which I plan to try in the coming months.
Regarding the latter group, I can think of
Creative's Super X-Fi technology, which I tried (namely I had and tried their Sound Blaster X3 USB unit). I did not find what Super X-Fi brings to the table better than previous efforts. I am speaking here about the listening experience of audio contents processed with said technology, mainly in the form of movies or games. What I remember the most is the bloated low frequencies I got, which made the audio not clear enough.
Another solution which uses optical measurements of one's ears is the new software for gaming
Immerse Gaming Hive, which has got some promising reviews very recently. I have not tried it and I do not have the intention of doing so though.