def wait_for_condition(obj, cond, timeout=None):
  """
  This is an extended version of #wait() that applies the function *cond* to
  check for a condition to break free from waiting on *obj*. Note that *obj*
  must be notified when its state changes in order to check the condition.
  Note that access to *obj* is synchronized when *cond* is called.

  # Arguments
  obj (Synchronizable): The object to synchronize and wait for *cond*.
  cond (function): A function that accepts *obj* as an argument. Must return
    #True if the condition is met.
  timeout (number, None): The maximum number of seconds to wait.

  # Returns
  bool: #True if the condition was met, #False if not and a timeout ocurred.
  """

  with synchronized(obj):
    if timeout is None:
      while not cond(obj):
        wait(obj)
    else:
      t_start = time.time()
      while not cond(obj):
        t_delta = time.time() - t_start
        if t_delta >= timeout:
          return False
        wait(obj, timeout - t_delta)
  return True