Want to set an alarm via OS X terminal? It's easy, just use this!

alarm.sh

#!/bin/bash

# Simple script for setting an alarm on Mac OS X
# Arguments are ./alarm.sh {hour} {minute}

until [ `date "+%H"` -eq $1 ] && [ `date "+%M"` -eq $2 ]; do
  sleep 10
done

osascript -e 'set volume 7'
say -v Trinoids "WARNING WARNING WARNING"

On an Ubuntu-flavored machine, the last two lines could be changed to:

amixer -c 0 set Speaker 100%
espeak "WARNING WARNING WARNING"

Though no promises that it works on your particular machine.