[Extremo]

If you're looking for remote file inclusion vulnerabilities, javascript injections, SQL injections or any other known vulnerability, you're going to have to look for it on your own. No one here is going to help you and tell you whether some website you don't like has a vulnerability, or whether the URL inputs are sanitized or not.

EDIT: If you're looking to remotely send text messages to that site, simply POST your own form to their respected pages and simulate user-input.