I have a Marco Polo tracker on my Mavic 2 Pro. Haven't had to use it yet but I had one on my Phantom 3 Standard a few years back and had to recover it from a crash. I knew the general location of where I crashed in a forest area so as I searched for it, the signal popped up and I was able to find the P3S in no time. As far as a fly away, you would definitely need to know the general direction of which way it went because the Marco Polo has limited range. I haven't had any experience with any GPS trackers. If they have any free ones, I wouldn't mind looking into it but as of now, I don't want to pay for any subscriptions for one.
