Please note that you can't have a script that literally "never missing a heartbeat", since the script won't work if you're disconnected.
However, aside from the condition that you must be connected, I think the above script will work per your request.
You can actually never miss that heart beat :P
timer -o DATAHOUR DATAXTIMES DATAINTERVAL COMMAND
will create whats called a offline timer meaning that should it occur the user is disconnected or something the command will still work or the timer in question I should say
