This will make total sense for anyone who has fallen asleep at the wheel (or during 3rd shift at work etc): an alarm clock (or alarm application for cell phones) would provide a function where upon activating it would go off at random intervals and continuously reset until a predetermined time.
Subideas: 1) Alarm changes between sounds so it does not become too recognizable.
2) Require the user to perform a simple logic puzzle (like completing a pattern) in order to turn it off (IE prove they are still awake)
3) The function times the user's response to the alarm. The longer the users response is, the earlier the next alarm will sound.-- gomer, Jul 25 2008 I saw a show that they are testing glasses that do this a bit better. They use IR sensors to sense length of eye blinks and alarm if they exceed a preset value.-- MisterQED, Jul 25 2008 random, halfbakery