I have just put my latest paper online that I wrote for university: Building a Portable Low Cost Tangible User Interface Based on a Tablet Computer.
It has evolved from the idea, that recent tablet computers like the iPad, that are equipped with a camera, can be used to create a table-top Tangible User Interface (TUI) providing an user interface physical objects to interact with. Such a device can be used for games, education, museums and so on. It is independent from an external power source since it runs from battery power and in contrast to existing TUI devices is cheap, low-weight and therefore portable. To achieve this, the open-source computer vision framework reacTIVision has been utilized and was ported to the iOS platform so that it runs on Apple iPads and iPhones. This modified version was named iReacTIVision and is available on github.