Bill My Parents (http://www.billmyparents.com)

There might be a good application of this site, because it keeps the actual credit card number out of the hands of the teen, and monitors the purchases before they are officially charged. In practice, however, the mental and emotional hit a teen may get from just going through the process of making the purchase online and the subsequent headache the parent will get from having to say no will likely be more of a hassle than a help. Perhaps for college kids who are away at school, this might prove to be an efficient means for parents to keep tabs on expenditures -- and may be easier to say no from afar.