Hi Paulo,
I´ve made some interactive floors using Openframeworks.
The process its not very difficult :
1. Grab data from the Kinect.
2. Set minimum and máximum thresholds. (Checkout ofxKinect exampple for this).
3. Gran the OpenCv example and use the thresholded image with the contour finder. These will give you the blobs you need. Try using the gui examples so you can play with the parameters of your app like Threshold, Blur, contourFinder minblobSize, maxblobsize, etc.
4. Once you have the blobs on an array you can use the blobs centro id so you can create a Particle system using those coordinates.
In the reference video every particle has its origin coordiante and if theres a blob position near (lets say 300px) you set a repulsion force for the particles.
Check out "The nature of code" for creating these type of visuals.
Hope it helps.