Those can be good, not sure how reliable they are, and of course you've got to send it to the right carrier. I'm volunteering for a non-profit right now on a p

Those can be good, not sure how reliable they are, and of course you've got to send it to the right carrier. I'm volunteering for a non-profit right now on a project that sends SMS messages through Twilio, I think their current cost is $0.0075 (for a US to US message), and interfacing to Twilio is easy, if not a joy, their API is sane and the on-line documentation is excellent. This approach gives you the whole 160 character budget to describe the problem.