As David Bisset for BP-Test, i wrote a very basic component for BuddyPress called bpdev-example that you can find in the on its page http://buddypressdev.org/plugins/bp-example/
This isn't really a plugin but is a starting point for developers.
If you've question about it, ask here. As soon as possible I'll write an HOWTO for it.
Bye for now,
Nicola Greco