Airbook and mobil hotspot like iPhone

We are traveling and I want my Macbook Air to access the internet like my iPhone 4 does. I use Lion and AT&T. If I buy a mobile hotspot for the airbook, and get a data plan will that give me internet everywhere like Iphone even in the car on the road? MiFi Liberate has been recommended. Oh yes, will it also work for my iPad mini?