o kernel bug (?): TIOCMIWAIT ioctl may wait on a port that is shutdown
  by serial driver.  A fix suggested for now (serial.c):
@@ -1074,6 +1088,7 @@
 #endif

	save_flags(flags); cli(); /* Disable interrupts */
+	wake_up_interruptible(&info->delta_msr_wait);

	/*
	 * First unlink the serial port from the IRQ chain..
@@ -2000,6 +2015,8 @@
				cli();
				cnow = info->icount;	/* atomic copy */
				sti();
+				if (cnow.rng == cprev.rng && cnow.dsr == cprev.dsr && cnow.dcd == cprev.dcd && cnow.cts == cprev.cts)
+					return -EIO;
				if ( ((arg & TIOCM_RNG) && (cnow.rng != cprev.rng)) ||
				     ((arg & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) ||
				     ((arg & TIOCM_CD)	&& (cnow.dcd != cprev.dcd)) ||

o New command:
  dialer phone-number #times [modem-dev]
  Account for local PTT differences as much as possible (possible?).

o Allow specification of day-of-week & time ranges for each rule;
  eg: 035;1000-1230,2300-0000

o Identify call waiting if phone is busy (if it is data/fax-busy call
  waiting should be normally disabled - so no way to identify).