In third or first person you can do this "wallhack" by standing or kneeling next to a wall of a building, taking out your fists or any weapon you have, and lean all the way back. If you are up against a wall you will go through the wall a little. When you do you can hold down alt by looking around and see everything that is happening outside. I have no clue if you already knew this or not. I found out by accident looking up at some stairs while against a wall. I didn't use youtube for the video because if people don't know about this I don't want it being spread around. I also set this to private.

https://www.dropbox.com/s/5y6q11ujm6ekb4i/DayZ%20in%20game%20wallhack.mp4