Ferrowatch is a wrist watch concept, by French designer Karim Zaouai, that uses a material called Ferrofluid to tell the time.
Ferrofluid is a fluid metal that becomes highly magnetized when exposed to a magnetic field. Under the liquid watch face is a regular watch with magnetically charged hands that force the Ferrofluid to react, allowing the user to see the time.
Via Designboom.