SPOnG believes that these are the first images of the thumb pad controller for the Nintendo DS, the little nodule that was displayed during the presentation of Super Mario 64 DS in Seattle last week.
After the briefing to press, we nipped down to the front of the stage, got permission and snapped away, though lighting and the fact that we had only about three seconds didn't make for particularly good quality shots.
As you can see, the thumb pad comprises part of the wrist strap that will be bundled with every Nintendo DS.