Relevant references and citations — with detailed annotations — provided to TED by Fabian Hemmert.
Fabian Hemmert et al., "Weight-shifting mobiles: Two-dimensional gravitational displays in mobile phones," CHI 2010, April 10–15, 2010
This is an article about the first prototype.
Fabian Hemmert et al., "Shape-changing mobiles: Tapering in two-dimensional deformational displays in mobile phones," CHI 2010, April 10–15, 2010
Here's the second prototype.
Fabian Hemmert, "Life in the pocket — The ambient life project: Life-like movements in tactile ambient displays in mobile phones," International Journal of Ambient Computing and Intelligence, April/June 2009
This article is about the third prototype I discuss. There are actually loads of publications on the prototypes, but these are the primary ones.