I agree, that's the easiest crude way to do it. The only problem will be is if you're trying to make an app where people supply their numbers in order to get a

I agree, that's the easiest crude way to do it. The only problem will be is if you're trying to make an app where people supply their numbers in order to get an SMS, because you don't know the carrier. To get around that, afaik, there is: 1. [hard to implement, and costs money, easy for the user] integrate with an sms gateway. Here is a comparison of two: http://dcwilkie.wordpress.com/2010/11/12/sms-gateway-comparison-smsglobal-vs-tropo/ http://dcwilkie.wordpress.com/2010/11/12/sms-gateway-compari... 2. [easy(er) to implement, free, hard(er) for the user, hacky] Have the user sms a user id (or some identifier) to an email address, you read that email, and associate the identifier with the "from" field, and send sms's to that email.