As many others said, I don't think <call#> is needed.
There are other much more effective ways in making sure everyone is ready for content. If someone is not there for a long time, there is a pretty good reason for it and "calling" him would be pointless. Also, you'd want to get a replacement for that person anyway.

So, no thanks.
A /readycheck or /away <message> would be more effective and less disturbing.
If call get implemented, it definitely need a turn off option in the sound menu (I want to enjoy the music, not a whistle chorale).