[interfixus]

That was my thought, too. Day to day, my phone alarm is fine (and I damn well tested it thoroughly before actually relying on it), but if anything life-and-death is scheduled, I'll use at least one independent extra device. And all this even though I always wake up on time and never am late. Likewise, the phone call problem has an easy solution: Assign different sounds to different callers; low and unobtrusive to the unwanted ones. And the delivery: Never trust such a thing without sufficient fallbacks. If you want safety and full control, organise the thing yourself. All in all, I get a vibe that the poster may be a wonderful coder, but really hasn't got the paranoid mindset required for mission critical work.