Two articles on Benchmark Hunting.

Benchmark Hunting
http://www.geocaching.com/mark/

Forget Geocaching, Bench-Mark Hunting Is the New Nerdy Hobby
http://www.wsj.com/articles/forget-geocaching-bench-mark-hunting-is-the-new-nerdy-hobby-1430493593

While this may be new I can remember doing this back in the late 1970’s, that is finding benchmarks because back then we did not have GPS to confirm the location. Back then we just had a quad map with the printed location of where you might find a bench mark and you used your map skills and senses to find these obscure objects on/in the ground. It was fun and tested our map skills and ability to find something shown on the map in very remote locations.
One of my early finds of a bench mark that I recall was in the Wind River range of Wyoming. We stumbled across our first one more by accident that on purpose and after that we set out to find all the ones we could that were near to where we were going. We found all the ones we were looking for.
My wife sometimes thinks I am crazy as over the years our vacation photos almost always include survey monuments from various locations. It is something I have always done it seems like. Now with GPS though taking a shot of the benchmark/survey monument can also include a GPS unit sitting next to it to validate it’s location. Also with sites like the Geocaching site you can now document the monuments you find. What fun and a way to get out and explore the great outdoors.