You can kind of do this already, just with the standard /tell sound. Just use a macro with a time delay (pause) line.Consider adding a feature for macros that adds a command for an audible chime or sound from the UI sounds.
For example, a command named "/notification" with a few keywords like "jawa", "tusken", "wookiee" that makes the audible noise of each respective keyword when a macro reaches that line. Like /notification jawa;
A potential use-case of something like this would be if you were grinding trader tokens, you could have a macro that pauses for 15 minutes and at the end of the 15 minutes, it plays a sound at the end to hopefully get your attention that it's time to make another token. This is how I would use it anyway.
I hope this makes sense.
/pause 10; (number of seconds you want to wait)
/tell (character name) (the message);