TUIO is an open framework that defines a common protocol and API for tangible multitouch surfaces
TUIO is a simple yet versatile protocol designed specifically to meet the requirements of table-top tangible user interfaces. Inspired by the idea of interconnecting various existing table interfaces such as the reacTable, being developed in Barcelona and the tDesk from Bielefeld University, this protocol defines common properties of controller objects on the table surface as well as of finger and hand gestures performed by the user. Currently this protocol has been implemented within a fiducial marker-based computer vision engine developed for the reacTable project. The TUIO protocol has been implemented using OpenSound Control and is therefore usable on any platform supporting this protocol (from OSCulator user manual).
Source: http://www.tuio.org/ (consulted 2013)