So, turning people into stone. You only have to add reversibility to the mix, and it becomes the BEST paramedical tool available.
But, what does petrification need to accomplish to become just that?
Well, it has to "freeze" (read: prevent its molecules and cells from decaying) the body as it was as fast as possible, starting with the brain, as that's the one thing you can't replace. This will most likely be done by nanomachines, son. It's also pivotal for the frozen body to remain stable for long enough, even in harsher environments.
I wanted to resolve that issue with a "mantle" of utility fog that would condense around the body and give it that stony texture, but I keep that for another question.
Now, I know the criteria, but I don't know one important thing. How would the nanites be able to "freeze" an animal's body?
To be clear, the tissues don't fossilize. As far as the exact method goes, I've no clue, that's why I asked the question. You don't have to take even freeze literally. If there's a method that accomplishes the points in the criteria (preventing the cells from decaying), that's good enough.
Oh look, I found a useful link: