I have an idea for a website that I am working on and I am looking for a service I can use to automatically send registered users text messages when new information has been added to the site that is relevent to the user.

The service would need to work online and charge the end user a premium rate for recieving the text message, of which I would recieve a percentage.

Can anybody recommend / point me in the direction of a company that can offer this service?

Ideally, I am looking for minimum initial outlay to set up this service and obviously the maximum return rate of the text premiums.