One nice feature of some Android phones is the ability for apps to choose from a few different colors for status light notifications. Facebook flashes the LED in blue and Evernote flashes green to notify you a note has been synced — subtle touches that convey useful information about app activity.
Along these lines, it would be nice if the Google Talk app used a red light when you receive a message while your status is set to Away and green when Available. I feel comfortable waiting to respond to messages when my status is set to Away. You would have to turn your screen on to see which app triggered the light if you have several that use the same color, but it’s no different from every app using the default LED color.