I just wanted to mention the great Open Source multi-touch tracking application Touché for Mac OS X from Georg Kaindl in my blog.

Touché supports lots of image processing possibilities and is written purely in the Cocoa Objective-C framework from Apple. The Touché code can be accessed via Google Code. Touché supports loads of video cameras amongst others the Pointgrey Firefly MV.

Touché produces TUIO OSC messages and also the TUIO XML analog for Flash rendering FLOSC unnecessary.

As far as I have seen and tested Touché it has a slightly bigger latency than the Touchlib with an appropriate Touchlib configuration.

However, Touché seems to be the best choice for everyone, who wants to use Mac OS X for the tracking in multi-touch setups. It is highly cofigurable. Georg Kaindl is developing Touché on his own. Thus, there is only one responsible, friendly and very capable programmer that can be easily contacted.

The discussion about Touché in the NUI group can be found here.

Finally, here is a video of Georg Kindl showing Touché on Vimeo:

Touché 1.0b3 + LLP Table Demo from Georg Kaindl on Vimeo.

There are more videos of Touché available.

Somhow I must have missed this one: Microsoft published SecondLight.

This is a system that is able to project a second image through the tabletop of a multi-touch screen onto a sheet of paper or whatever you want to use. But take a look at this video:

Actually, this is great. Anyway, I would not know what applications could use SecondLight except the obvious magic lens applications. Thus, I embrace following cite from the according SecondLight engagdet post:
Like the Surface, practical applications for this seem somewhat limited — but since when have you cared about practicality?

I use my code in both an Adobe Flex and in an Adobe Air application. As I want to use the native menus of Adobe Air I want to prevent that my self-built menu is being added to the Air application. Thus, I need to figure out if the code is running in a Flex or in an Air application. I do this by using the following structure:

var airApp:Boolean = false;
try{
if(NativeApplication.nativeApplication) airApp = true;
}catch(error:Error){}
if(!airApp){
addChild(generalMenuSprite);
}