PHP 5 class that implements listeners for managing out going bulk SMS to the text marketer gateway (it could be adapted for others). Your 'listening' class must implement 2 public functions which get called (or notified) when an error occurs or the credit level threshold has been reached. The api requires an account (free) which you can get here: http://www.textmarketer.co.uk/free-bulk-sms-software.htm There is an example of a listening class in the text file that contains the SendSMSNotifier class