Ever since I found Reactables, I've been intrigued.
Bridging the physical world with digital environments seems very promising in enabling new types of interactions for individuals and teams alike.
Being able to recall (read) and modify (update) data from a tangible, shared interface creates many new opportunities for interaction. The use case that comes to mind is bringing strategy planning sessions to life. By using live physical objects in a planning session connotes a longer life, where the objects can be measured, revisited, and perhaps updated over time, rather than re-planning fresh each year.
Reactivision and TUIO
Reactivision is a framework built atop TUIO.
Reactivision is a visual image recognition software. It is responsible for reading a video stream and interpreting multitouch events to a coordinate system.
Other software is responsible for interpreting events and projecting motions images based on those events.
[update Jan 2014]