This is a success and has been waking me for the past couple days. I really wanted it to get more exposure so I could collect a variety of interesting alarm sounds. Thus far I've been awakened to MadCow.wav, "Parental Guidance Strongly Recommended", and Jeff Goldblum's creepy laugh from Jurassic Park.
The setup for this is really pretty simple, and the YouTube video covers it well. A basic PHP website collects user input via HTML form. These files are then processed by SoX into .ogg files for playback.
One "tester" tried repeatedly to break the system by uploading sub-bass and ultrasonics, which led me to make changes to the SoX command line to attempt to prevent silent uploads. I used one of those YouTube frequency response videos to find the range of my speakers, then set up SoX to have highpass 120 (-6dB at 120hz... I think...) and to resample to 32khz which stops anything over 16khz, thanks Nyquist!
This still had some issues so after normalize I did another pass with a 120-8000hz bandpass and checked RMS levels. Anything below -21 is rejected as "too quiet". These values aren't highly scientific but they do let most of the good stuff through, so I'm satisfied.
One final step is VorbisGain application. Even though all files are normalized, they aren't equally "loud". I took a sample and boosted the volume into clipping range as a test, which was very loud and annoying. VorbisGain puts ReplayGain info on every file which keeps them at the same relative volume on playback, so I don't need to futz with the volume knob any more.