as requested by Peppe I presents what we are doing with blender.
In addition to traditional modeling usages we are using a modified blender version for experiences on 3d manipulation and gesture based interaction. This version is called blenderTUIO as it provides tuio and osc support and exposure to the game engine sensors. This allow us to quickly realize prototypes and experiments without bothering too much on coding details. It is an hard work to keep this version synchronized with the official 2.5/alpha1 branch but it is working.
We were allowed by the institute to release our code and you can find:
more infos:- http://forge.lifl.fr/PIRVI/blog
.exe to download:- http://forge.lifl.fr/PIRVI/wiki/MTUtils/blenderTUIO
For linux version you need to compile it yourself, just ask for a svn access to download the sourcecode.
Recently we spend some time on implementing screen space based 3d manipulation (what I believe is the good way to go for direct interaction on touch table devices). This was done in blenderTUIO using the python scripting feature and the python binding of the levmar minimization solver (it was not working out of the box and I had to adapt it, send me an email if you want to use levmar within blender).