The real-estate next to your bed.

I put my iPhone in Airplane Mode and Silent Mode, and set an alarm to wake me. Works great :)

I use my cell phone (as a backup for the alarm clock—I'm a heavy sleeper—or while travelling—when I don't trust the provided one) for this purpose, but get around the problem of its disturbing me during the night simply by turning it off. My cell phone will wake for the alarm; it's not particularly recent or sophisticated, so I imagine that most will do the same.

Hmm, that is indeed a good reason but on the two occasions anybody has called me at night it has been for good reasons and with information that I needed to know the next morning.