The SMI one, and the accompanying Nvidia foveated rendering demo.

Were they in VR headsets (or glasses), or were they the desktop bars?

(Last time I tried a bunch of eye tracking, the desk-mounted was amazing and the head-mounted wasn't)

They were inside the headset, lining the lens, such that you couldn't tell between a normal Vive and an eye-tracking Vive unless you cracked it open.

Amazing!