Leo says that would be a great option. There are some apps that could offer that, but Apple doesn't give third party access to the text message system. There are security issues in allowing third party access to text messaging, which is why Apple doesn't do that. Ray could jailbreak his iPhone to do that, but Leo doesn't recommend jailbreaking.
T Mobile offers something similar, but they don't carry the iPhone (yet). Android does have this, though. So if he's not married to the iPhone, he could switch to an Android phone.