IPhone – receive messages sent and received from another iphone on the account

In iOS 6, your phone number and your Apple ID will be unified, so when you'll receive a iMessage or a Facetime call, they will appear on all your devices (iOS and Mac OS).

More info here.

So I think you just need to wait until this fall to resolve your problem !

Check the following:

1. Settings
2. Phone
3. Click the third line (free translated) "Answer with text message"
4. The exact text you received is right there.

If you have a running phone call, your screen will turn black once the sensor will notice the darkness of your face being close to it.

Once you click on your phone during an incoming call, you can decline the call and answer with one of the messages explained above.

This has nothing to do with spying and hacking.