Watchdog credits
Control Panel > Watchdog Settings > Cell Phone Credits

The Web-Stat Watchdog can send SMS text messages to your cell phone in case it detects that your site is unavailable. This will allow you to react immediately to any event and minimize your site's downtime and lost revenues

Each SMS text message costs $0.49 to send ; in order to enable the text message alert service, you need to make sure that your Watchdog SMS account contains enough credits, if not you can easily buy some from the Control Panel.