When I got my belt I wanted to share it on Facebook. I think a FB app would be really good for that! ;)

I know I can post a status message manually but I think people an app post with some kind of little graphic of a guy wearing a white/yellow/orange/etc... belt doing a flying kick ;-) would generate a lot of interest in people to find out what it is all about, especially when they see our progress throughout the belts (also because it would look fun, too, rather than a heavier "I got this work done today" vibe).

In case people are worried about annoying friends, you could allow the visibility to be set via the app, but also I think the belts are spaced out enough so that posts won't become annoying (as some game apps are).