Just something like the GW2 icon doing that generic orange flash thing or maybe an optional noise. This would be so amazing for long queues when people don’t have much to do while waiting and would rather tab out and watch videos or something instead of tabbing back in every 30 seconds.
Made a Reddit thread, too.
http://www.reddit.com/r/Guildwars2/comments/10cfoa/can_we_get_something_that_alerts_us_when_an/