Mobile Phone Site

[Yug]

I am a good way through the development of a mobile phone adult site with a friend of mine who is very well versed in the area of mobile phone technology. He has the skills and experience when it comes to anything relating to mobile phones, i have the abilities when it comes to creating a web medium for it and graphic design.

Forgetting about the traffic side of things (thats another topic entirely that while more important than this, its not what i want to discuss here), I would like to know what anyone here knows in regards to billing mobile phone users.

We have put together a business model where the user would be able to access the photos/movies either via their mobile phone browser of the net, and then either download a single image, a complete set of images, or have a monthly subscription to the website in general.

Now please, I'm not after people voicing how stupid they think mobile porn is because of hte small screens, etc etc. I'm trying to find out legitimate options in regards to billing.

Premium SMS and Credit Card Billing are the two main ones. Does anyone know, or has anyone ever heard of a credit card billing system that is capable of making a secure transaction via wap? Are there billing companies out there, adult specifically, who already offer a premium sms recurring revenue based service? And if so, what countries?

Cheers.