As other people have said, the MFMessageComposeViewController class is used when composing text messages for apps. This class can
"configure the initial recipients and body of the message, if desired,
and to configure a delegate object to respond to the final result of
the user’s action-whether they choose to cancel or send the message"
What this means is you can configure the class to respond to whether the user wants to send the message, or cancel it.
Before you use this class, however, you must call the canSendText class to make the sure the device can send a text or not. If the canSendText class returns a value of NO, then do not show the message composition view. That way, your app doesn't try sending a text with a device that cannot send one (i.e. iPod)
According to the documentation by apple, you must make sure that
" If neither iMessage nor SMS/MMS (Short Message Service/Multimedia
Messaging Service) delivery is available, you can notify the user or
simply disable the messaging features in your app."
Hopefully this helped you.