Steve Wadsworth, the President of Disney Interactive Media Group, recently let slip during his keynote speech at the 2010 DICE summit that the new Sony motion controller is called the "Gem". This slip was made during a comment about upcoming software design opportunities with next-gen console peripherals like the Xbox 360 Natal and the Sony… AHA!
EA’s CEO John Riccitiello made a similar slip this past December at another conference, calling the device the Gem also in reference to next-gen peripheral software. However, the device is also being called the Arc fairly widely within the game journalism community, and Sony has yet to confirm or deny either name. Word on the street is that Gem was at least a codename used during production of the device, if not also its ultimate shelf name.
More to come on this, and probably a definite answer, at GDC this spring.