I'm happy you got it working, but there one thing more you would want in your case scenario. Script will not start when vps will be for whaever reason restarted.*
You can try supervisor like below. I would be thankful if you would ping me back and tell if it's working (why? see *).

# Instal the supervisor
sudo apt-get install supervisor

# Make a conffile
sudo nano /etc/supervisor/conf.d/datacoin.conf

# Paste there this, should work... Fat manual: http://supervisord.org/configuration.html#program-x-section-settings
[program:datawatch]
command=/patch/to/datawatch.sh pool mode
stdout_logfile=NONE
stderr_logfile=/patch/to/logs/catalog/%(program_name)s.log
autorestart=true

# Restart supervisor daemon
sudo /etc/init.d/supervisor stop
sudo /etc/init.d/supervisor start

There will be one additional logfile with stderr as you see. Could be set to NONE too, but one more file containing eventual errors doesn't hurt (and might sometimes help).

*It's a bug and feature BOTH. I mine with my pc only, as I don't have credit card/paypal/etc so I can't even try the free trials outthere, and if my pc goes down for whatever reason I want to inspect it manually, and for sure I don't want to automatically stress the machine (in case of cooling faillure for example).