If you hit send, then it will only be pure luck if you are able to catch it before it gets sent out. Remember that SMS uses the the cell connection and not 3g or 4g service to transmit. It goes pretty fast, and the only way I think it might get stopped is if you actually corrupt the message as it is going out.
Yeah i wondered this too and i dont know why its not implemented on a smart phone. The old featurephone(or dumbphone) i had would let me cancel a message by either hitting the back button or end button.