Touchlib is a blob-tracking application. It takes the raw feed from the webcam and by applying filters, produces clean blobs. It then outputs this blob data in TUIO format (see this thread for more info: http://nuigroup.com/forums/viewthread/1495/), which can be relayed to flash applications using OSC/FLOSC - see that thread I linked to for information on how/why this is necessary.
Once the blobs have been tracked and relayed via TUIO, you can write applications that the blobs can interact with - this can be done in many languages; AS3, C++, C#, and python are 4 popular ones to use, and have some level of documentation/frameworks that you can use. I guess you want to use C++, since you already know it - unless you’re open to trying out a new language.
See this thread for info on a touchlib helloworld in c++: http://nuigroup.com/forums/viewthread/1380/ . Note that C++ apps currently only work with touchlib, not tBeta (the new and improved cross-platform blob tracker, http://tbeta.nuigroup.com) .So if you develop your apps in C++, they won’t be compatible with tBeta, which most people are using, especially those on mac and linux.
if you’re good with C++ and want to go with that, then use that thread to get started - but if you’d like to try other apps, let me know, I can give you some more starter links.
hope this helps,