Once they're able to detect trails and follow them looking for people, the next step would be detecting signs of where they might have wandered off trail, or (especially in snowy conditions) detecting and following where they have started their own trail.
A drone that can follow a trail that changes quite a bit over the year and is trained to recognize obvious trail signals (jacket on tree, reflectors) or human voices offtrail as it passes ("help! over here!") would be excellent. A drone pass at closing time might become a standard precaution and CYA thing for parks, plus they can give trail notes like where it's poorly marked, blockage and collapses, and so on.
The only wilderness place I know that is 'littered with dead bodies' is Mt. Everest. And that is from hypoxia and exposure, not getting lost.
EDIT: Hmm, and maybe Aokigahara Suicide Forest in Japan. Also not from getting lost.