// file: sbbeep.c
#include <stdio.h>
#include <time.h>
int main() {
    struct timespec a={0,200000000}, b={0,600000000}, c;
    int i, j;
    for (j=0; j<3; j++) {
        for (i=0; i<3; i++) {
            putchar('\a');
            fflush(stdout);
            nanosleep(&a, &c);
        }
        nanosleep(&b, &c);
    }
    return 0;
}

Compile this tiny prog with gcc -o sbbeep sbbeep.c and move the resulting file to /usr/local/bin/sbbeep

Add something like the following to the crontab of root.

# Daily alarms at 8:57 and noon:
57 08 * * * /usr/local/bin/sbbeep > /dev/console
00 12 * * * /usr/local/bin/sbbeep > /dev/console

For unique alarms you can copy the following script to /usr/local/bin/sbsetalarm:

#!/bin/bash
# file: sbsetalarm
# An alarm clock
# Example usage: "sbsetalarm 17:10" or "sbsetalarm now +5 minutes"
# This script accepts the same time specifications as the 'at' command, because
# they are simply passed to 'at'. See "man at" for details
# Check already set alarms with "atq"
 
beeper='echo -e "\a"'                      # default noise maker
bebeep=$(which sbbeep)
if [ $? -eq 0 ] ; then beeper=$bebeep; fi  # try to find a better noise maker
user=$(id -nu)                             # get user id name
ltrs=$(find /dev -name 'tty*' -user $user) # look for allowed terminals
trms=$(echo $ltrs)                         # replace '\n' with ' '
term=${trms%% *}                           # take first terminal
#term=$(echo $terms | cut -d' ' -f1)       # take first terminal (alternative)
#eval $beeper > $term                      # test if alarm works
echo "$beeper > $term" | at "$@"           # call 'at' with your timespec