Sorry to say that there is no such thing as thief proof. You can make it more difficult for them by using good locks and cables, but if a dirt bag is determined to steal it, he is going to. Or at the very least tear it up trying.

What I do with all my stuff is put a little tag on it saying "Smile, your on candid camera", even though there isn't a camera there. If they look around and can't find a camera, they might decide to walk away thinking you have their picture.