Yay! I hit the front page of Hack a Day!

If you look at the readme, it explains in rough terms. If you have scratchbox set up, it's a matter of downloading the source package, changing one word in a file, and rebuilding it. However, I will be providing packages soon - it was 3am when I got this done, so I didn't bother right then. :P In the mean time, if you know how, just change the backend to "dummy" in the package's rules file.
As for displaying actual alerts on it, that's my next step. Be aware, though, that this is a non-standard hack, and is not something that Nokia is going to distribute. If any third-party application developers want to add a hidden feature to use this for those that want to, that would be cool.

Update: Rebuilt BlueZ packages are at the Files link on the blog post linked to from here. If you have an N900 and the bracelet, please try it out and let me know how it works