Someone mentioned this idea to me and I thought I'd post it here (vivoactive user). It might be something I'll do, but I thought I'd open it up.
Basically a way to record a list of locations while on a hike, so that if you get off the trail or if the trail is poorly marked, you can get back to a previous point. The App starts and get the first GPS location as "start", and then, either by a timer or user action, GPS locations are saved along the way in an array (each trail marker, every 5 minutes, etc), with the array holding a reasonable amount of positions.
Then, when you want to take the return route, it uses your current location and points you to the last saved position, and when you get there, to the location before that, and so on, until you get back to "start".
Kind of like the "return to start" function in walk or run, but more detailed, as the "as the crow flies" direction and distance could lead you through a swamp!