Some carriers open the ability to send an email to phonenumber@carrierNetwork. The trick is that it's difficult to tell which network a stranger has come from i

Some carriers open the ability to send an email to phonenumber@carrierNetwork. The trick is that it's difficult to tell which network a stranger has come from if you don't use the existing infrastructure that operators have developed (carrier-specific SMS gateways and inter-carrier SMS gateways). Carriers have a very effective lock, but the OP is right -- this is something that is ripe for new solutions as smart-phones become more ubiquitous. This doesn't address the issue for millions of other subscribers that can only use phones (mostly Nokia) that can never have 3rd party apps installed.