While facial recognition will be very handy once all of the bugs are worked out, a much simpler feature would be incredibly handy: Optical Character Recognition, particularly that of numbers on racecars, runners etc.
I have been photographing a few races and it would be extremely handy to have something like facial recognition that would work for car numbers, and possibly car class as well.
When photographing a foot race, where all of the number signs are of the same format, this would be very helpful for photographers looking for photos of a particular person on request.
Likewise when photographing an auto race, it would make it much easier to find all of the photos of a particular driver.
This would be SO helpful! Especially for "bibbing" runners at big races!