TUIO is “an open framework that defines a common protocol and API for tangible multitouch surfaces”. It is based in OSC (Open Sound Control), and used in Reactable-based solutions (http://www.reactable.com). The developers behind TUIO include Music Technology Group (University Pompeu Fabra, Barcelona) researchers but also external developers, as TUIO is an open framework. Some of these developers have implemented a TUIO/Flash library, allowing to better integrate Flash/AS3 with tangible multitouch surfaces (to allows to transmit OSC messages more efficiently).
Link to TUIO
http://www.tuio.org/
Link to TUIO for Flash:
http://bubblebird.at/tuioflash/