Gallium, Indium, and Tin can be used to create alloys that are liquid at or around room temps (depending on the percentages of each). I'm not sure why this is a good idea for a heat pipe setup though... I thought heat pipes used the liquid to gas phase change... None of these metals are going to go to gas at temps seen by processors. So I'm not sure how they are going to flow in the heat pipes. But then again I haven't read the Danamics' page yet.
Edit - ah, they use an electromagnetic pump..