Is there online service to verify registered users by SMS before users can buy or doing anything on some websites, like a bulk service that doing this service to avoid problems or fraud.
During registration you could have a verification code sent via sms. When user get the code they could verify their registration on your site. The Five Star SMS Script could be customized a bit to accomplish that.
http://www.review-script.com/forum/f22-five-star-sms-text-messaging-script/sms-text-messaging-script-2807.html
Hope that helps,
Tim