I've updated the command line utility https://gitlab.com/bettse/usbnotifierosx_cli and works with Mavericks (OS X 10.9).
I haven't updated this code, so it may not work with recent versions of Growl
I was able to get the USB Mail Notifier working with growl, and I've published the Growl plugin at https://gitlab.com/bettse/GrowlUSBMailNotifier
There is still more work that can be done (isn't there always?), but I'm quite proud of how well it works and the simple configuration panel it has right now. I use this daily as my default Growl plugin, backed up by the Music Video plugin, and I've even got it setup on my dad's computer as well.
While browsing a website specializing in products manufactured in China, I found a little USB device called "USB Mail Notifier"(model CVCW-K125) that lights up when you get email, or a message on Skype/MSN Messenger . I thought it was really cool because it follows my interest in Ambient displays. I decide to buy one even though it was clear that it didn't support OS X, which is currently the only OS I'm using. I did some research and found a couple projects that used python to get it working with Linux (http://code.google.com/p/usbmailnotifier/ and lamp.py(lost link)). Using these as basis, I figured I could get it working with OS X. I finally got the devices today and after finding some very useful code on an Apple developer mailing list, got a protocol utility working with it. I have plans to use Growl to implement the same basic functionality as the device had on windows (coming on/blinking on IMs/emails), but for now I've just got the simple utility available at https://gitlab.com/bettse/usbnotifierosx_cli