Great question — answering as the UphillTech team:
FYI Simplewire is now OpenMarket.com/MXTelecom.com There are a couple of free SMS gateways but they all attach a SMS ad in your message to pay for the cost. ZeepMobile is the one I hear about the most. As for paying there are a couple of solution but this all depends on your needs. Two way communication would require the end user to subscribe to your service. There are a few ways to approach this: Short Code: you could get your own (www.openmarket.com) or share with others (www.clickatell.com) You could use a new service www.twilio.com looks to be good but haven't tested it yet. If one way communication is all you need you could so something like email to gateway sms but then you would need...
Full answer by Phill Pafford: https://stackoverflow.stackexchange.com/a/4268040 (CC BY-SA 3.0).
Need it done for your business? UphillTech.
