I'd really like to see a very simple plugin for WordPress.com in Firefox. It would work in a similar way to the GMail Notifier Firefox extension.
Every time you received additional views, it would make a very small sound (like this maybe?) and every time you received a comment, it would make a slightly more prominent sound.
You could change the default sounds, choose whether to display in the toolbar at the bottom of the page, and choose whether to be notified for hits and/or comments. What do you think? If I had any programming skills I'd write it myself! Does anything like this exist already? (I know there is a wordpress extension, but it doesn't seem to do this).