Today I did some google research on what others can or can't do in my current field of interest (hand / finger tracking). Here is a summary of what I found:
1. One of the most impressive demos is the following:
Kinect Hand Detection By Garrat Gallagher
It features image library scrolling, image selection, translation, scaling and rotation and looks quite like Minority Report.
2. This one is quite similar to what I do:
Palm position tracking [OpenCV]
There is not much description but it seems to work well. I don't know how much is functionality that OpenCV already offers.
3. Not bad either:
kinect - fingertip detection
Offers a brief description of how it's done. Point 3 "approximate contours" might be something I could try.
4. One of the first videos I had seen. Doesn't detect fingers though:
Multitouch with hacked Kinect
5. Similar technique as in my solution:
Microsoft kinect with Delphi -- realtime hand and fingertip detection
But thinning does not seem to be working too well.
6. Some more links