The Sleep Remaining Indicator by Nirav Patel is about the simplest alarm clock that I can think of. Rather than using a complicated display to show the current time and when the alarm is to go off, his design shows a simple laser line that grows shorter as the time runs out. Ok, it’s a pretty simple concept, but it is also simple to build, using just a laser pointer and a slowly rotating servo. I could imagine a strange electromechanical hybrid of this that uses a varying water stream to make the laser line, or a more complicated one that performs a laser light show when it’s time to get up.
Sleep remaining indicator is minimalist clock