Flash 8 has a more advanced implementation of FSCommand now, its the flash.external.ExternalInterface class, you can check out the Flash documentation here:
http://livedocs.macromedia.com/flash...=00002200.html
Additionally, you can make a simple XML Socket and go through that, a few small applications do that such as SOS, which allows trace commands outside of the Flash IDE.
As for C++, I'm not sure how much documentation there is, but atleast in VC++ and VB it used to be incredibly easy to embed a Flash movie and call FSCommands, not sure about External Interface however.