Japanese Tsunami Stones

I read an NY Times article on Tsunami Stones in Japan. There's something about century-old stones with warnings on them instead of someone's birth- and death-dates on them that strikes my imagination. Some of the Tsunami Stones are so old, that the characters etched into them have crumbled away.  It's easy for me to imagine the spirits of ancestors hanging around the stones in their effort to speak across time.

As a speculative fiction writer, I have to ask myself how I would make a marker.  Would I use titanium? How deeply would I etch it? What would I warn my descendants about? Don't build your house here; there's an old landfill underneath? Hey, there's Cesium burried here?

Or would I make the stone out of Nanites!  Or would I make a ... oh! Hey!  Gotta stop blogging, just got a cool idea....