Programming experiment from 2008!! For those days when I really want to wake up I try and set my regular alarm, and then my special home brewed computer alarm clock I made a while back. When both of them go off in a blaring symphony of ear splitting sounds, I just sleep right through them. Haha.. Just kidding. No really. No this thing can get pretty loud if you crank up the volume on your computer.. I almost blew out the windows a few times.
I posted a version online for people to use for free, and if you use Flash action script 2.0 you can modify it even because the source is included. I’m not sure, because it has been a while, but I think you can also modify the mp3 files and replace them with your own sounds. Yup, pretty sure.. So if you had your favorite song in MP3 format and you are using the PC executable from the download zip, you could have it loop the song.. They just have to have the same name. So if your favorite song is named track_9.mp3. you just rename it to alert_0.mp3 and replace the sound in the folder. Probably want to back it up first though so you can get the sound back if you want, you can change the file to alert_0_UNUSED.mp3 for example.
My ‘special edition’ version at home has a speech feature where it can announce the time in my voice. Tis sweet, but I wish it would be a woman voice naturally as hearing ones own voice is generally an unpleasant affair. 
Maybe someday. lol.
Warning.. There is a bug.. I couldn’t figure it out before I moved on from the project. I think if you leave it running for more than a day it might get thrown off or something to do with my terrible time calculations. So as long as you launch it once a day I think it should work fine.
Here is the link to the zip with source files on flashkit.com ..
http://www.flashkit.com/movies/Utilities/Time/Digital_-Jonah_Sh-12074/index.php
I forgot to include an .swf flash export in the zip, so mac users would have to have the Flash program and compile into a .swf since there is only an .exe. Here is a version on my website that should work on Macs, excluding the iOS mobile devices such as iPhone and iPad..
Hopefully someone else finds this useful, especially anyone who is still using Flash for interactive design.. lol.
