Ask HN: Send SMS to users, charge for it

I'm making a new funny site (for sake of having some description, clown siting site), and one of the things that would be interesting to do is to allow people to send SMS to other people from our site - clowns sited in your area, watch out! I'm doing the site as a static site, although I can of course add as much backend as needed. So anyone have any links on doing something similar, because of monetary considerations I don't want to send unless I know I get paid for it.