Hi,
I am Laszlo Benke, from Hungary. I am C# developer.
I made a similar kinect program that you need. I controlled robot arm via body movement.
I tried to detect clench and release movement, but I think that was not the suitable idea.
I can recommend (instead of clench and release) to use arm clicking via poke. The kinect sensing contains the hand coordintes by default.
I can send you a video about my program testing if you are interresting.
Waiting for you answer!
Best regards,
Laszlo Benke