This is a rather trivial application I created, as a subset of a larger monitoring application, that keeps an eye on Dragon Go Server for me and lets me know if I have turns waiting. I prefer it to email notification because it's more portable and immediate. Here's a screenshot. By the way, my DGS username is coljac, feel free to challenge me.
It's not much, but I find myself using it all the time, so I'm putting it out there in the off chance it might be useful for you, too. This is free software, released under the Gnu Public License.
You need Java installed to run this application.
Send all complaints to coljac (@) coljac.net.
Windows
This version uses windows native code to place an icon in the system tray.
You might want to have a look at the instructions.
All platforms
Pure java implementation, tested on Windows and Linux. Just run the executable jar with java -jar monitor.jar. You'll need to edit the monitor.properties file before running.