One practically free option is to have a strobe light app installed on your mobile phone. Some of those apps support the "SOS" pattern. It doesn't help much during daylight, but after the sunset light beacons are very effective. Even on the bottom of a ravine, there's a good chance that strobe light will be visible to rescue boats / helicopters.
Obviously, that works best if you could reach the rescue services and they are looking for you.
Another cheap (but not free) option is an online GPS tracker. Since it uploads your GPS coordinates regularly, it provides useful data even if fall somewhere with no GPS coverage: the coordinates of where you were before the fall.