What is that sign on heroes? And what does it mean?

Question

The sideways "S" with lines on it. The sign on the Haitian's necklace.

Answer 1

The symbol is called helix by the writers of Heroes. The symbol means "Godsend" (or "God sending great ability")
It also appears:
formed by flotation devices in a pool at a crime scene
scrolling in Chandra Suresh’s program
in a drawing by Peter Petrelli
in Isaac Mendez’s paintings
on a post-it in Mohinder’s apartment
on a geometry textbook owned by Claire Bennet
on pictures in Sylar’s apartment
on Niki’s back whenever she becomes Jessica
on future Hiro’s sword
on Chandra Suresh’s book, Activating Evolution
on Wonders!, the comic by Isaac Mendez
on the Haitian’s necklace
on a Greyhound bus

Answer 2

"somehow linked to evolved humans."

and may mean "godsend" Several pictures, and also appears in some graphic novels.