I've discovered the following useful trick for long-running tasks on the command line:
do_some_task && make_a_noise
For instance, on OSX:
do_some_task && say 'done'
&& means "run the next command if the previous one returned 0 for success". If the first command fails, the second doesn't execute.
Is there a similar operator that means "do this regardless of the previous command's return status"?