Message stones have been around for a few years and became quite popular. I know people who collected all the various words or sayings they could find, but most people pick out a particular stone with a specific message for someone.
One particular one that comes to mind was a young woman whose mother was being treated for cancer. She chose the stone that said "HOPE". Other's like "heal" or "pray" for those situations.
I know of one set of grandparents who bought several various stones and passed them onto grandchildren as rewards or encouragement.
Each stone is unique. These are not mass produced. They are river rocks that are various types of stone in various sizes and colors. The words are engraved, not painted. They're actually very nice. For those that remember the Pet Rock, this is better. At least it has a purpose. You can use it as a paperweight, if nothing else comes to mind.
There are also larger stones that say things like "Grow Dammit", which seems to be popular with gardeners. I could use one of those myself. Talking to my plants has been a waste of time. Perhaps they need some solid encouragement that's there 24/7. If that's the case, I need to get one soon.