I remember reading a comic with Daredevil in it once, that stated if Daredevil heard your heartbeat once, he could track you anywhere. Maybe it's a combination between sight, sound and smell, as well as tech. Something that lets them tell the difference between their prey and bystanders.
At current we humans have a level of tech. that lets us emulate a lot of the Predators abilities. Posibly a story
involving a Splinrt Cell/ Metal Gear type of super spy stalking a Predator while it stalks other humans or
maybe re-conning the Pred. homeworld, flipping the script some what.