The MessageUI framework added text in 4.2, if I remember correctly. I do not understand why this will not use iMessage in 5.0.
You will want us the MFMessageComposeViewController from MessageUI.framework. You can find all the methods on this apple developer documentation page, however you will need to log in with a registered developer account, as it may contain pre-released NDA products.
It cannot send iMessages instead of / sms' texts yet (I say this since I did not look), but should it do in the future?
Hope this helps.
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