Ok I just read
eye control - Canon
"Theoretically, this "eye control" can detect where your eye is looking at and pick AF sensor closest to what ever you are looking at.
Why theoretically? Because I never find eye control to work well. Not on EOS-30 (Elan 7e), not on EOS-3.... "
PBase • View topic - what is eye control
eye-start autofocus - Minolta/Sony
"way that most of the bodies in Minolta's line-up activate the viewfinder displays and autofocus. Activating a combination of two sensors (one at the eyepiece, one in the handgrip) turns on the camera, something that ordinarily doesn't happen until you partially depress the shutter release."
http://photo.net/equipment/minolta/greely/compare