I’m actually not using his code, as I found that Google has a simple badge deal available from them that I could just slap in the sidebar. However, looking for this was a needle-in-the-haystack proposition, and looking at his blog (and chatting with him) confirmed that this would work.
What’s cool about it is it’s anonymous both ways. I don’t have to expose my Google-ness to random visitors on the web, and if it gets annoying I can turn it off. Also, and most likely to be actually useful, people I actually know can go to my blog, check my status, and ping me if I’m around, all without downloading a client. On their end, Google is just running a web browser session for them. They don’t even need a Google account.