First idea posted here. Chew me out.
A set of old-fashioned padded headphones that cancel out as much sound as possible, preferably using anti-noise technology or some similar devices. However, also built into the anti-noise headphones, on each side, will be a small ringing alarm audible enough
to be heard and be quite annoying without causing damage.
A small digital clock set into one side of the set allows one to set the alarm for whenever they want. Also, an optional plug could be used to plug into any music-playing device. Another option is built-in, preset sound, at a level conducive to rest.
Practical application: 1:00 AM. A college dormitory, or a home by a freeway, or anywhere else where noise is prevalent. Eyes wide open, and streaked with red. Staring at the ceiling. Ears continually barraged over and over and over again by the noise, which is starting to sound like Cthulhu telling you whatever's on its mind right now.
Or, if you prefer, soundless, pristine, undisturbed rest, until the small alarm goes off telling you that your life needs getting on with. If the alarm weren't built into the headphones, you'd never hear it, as the dampers would prevent it from ever reaching your ears.