Nicer way to wake sit-for up?

[spamfilteraccount]

I have a code where the command loop executes a command which is
waiting for arriving data with sit-for. When the data arrives from the
network a callback is invoked and I wake sit-for up with a dummy event
like this:

the callback:

  ...
  (setq unread-command-events (cons 'data-arrived
unread-command-events))
  ...


the command:

  ...
  (sit-for 5)
  (if (eq (car unread-command-events) 'data-arrived)
    (setq unread-command-events (cdr unread-command-events)))
  ...


It works, but feels a bit clumsy. Is it a simpler or nicer way to do
this?