This one is pretty self-explanatory: an alarm clock based on the ‘Time Coordinates’ input device from Back to the Future. This would include a dimmer for those irritated by light while trying to sleep (I can relate). It would be smart enough to display the next day for the alarm, but if you need it to skip a few days forward (like when you don’t want to wake up on the weekend) that should be easy to do.
(UPDATE Dec 6/2013: the above is an updated render. Originally this featured a cord that tethered into an iOS device but I got rid of it!).