iPad and Macbook Secure Backpack

I'm not entirely sure if this is where this is suppose to be going but i was wondering what, if any backpacks that people knew that were fairly secure. I'm gonna be going to college next year in a town that has a fairly large amount of people and i'm going to be carrying a macbook, iPad 2, and an iPod Touch 4G probably most of the time. There combined value is about as much as my car, haha. So i was wondering if there was any backpack that kinda secure my stuff semi well. I know thats kinda vague, but i'm hoping that you guys will fill in the grey areas. Any answers will be greatly appreciated.