Hmm, from what I've read you need a licence - the networks won't give you this - just as KK says. You'll probably find that the cost per SMS will be too high to consider. You're probably better off buying a service, although that probably defeats the object of what you're trying to achieve.

If it's not free then why is there an open source script for this protocol written by the founders of SMPP? You can check their website at http://opensmpp.logica.com/

The ability to use the protocol is free, the ability to use the cellphone companies towers to send your messages is not.

Now I get ya. Because that's why some phone companies have better mobile coverage than others. Because they only own certain towers where as I would own no towers which means I would get zero reception and that's useless. O'well, it was a nice idea while it lasted.

Please note that the free SMS gateways both seem to be in India. way2sms appends advertising onto text messages that they send. 160by2 may do the same (that's why it's free). User beware.