Cell Phone Repeater

My husband works in agriculture, and his business has many different buildings that he has to work in. Unfortunately he has found that doesn't get good reception when on his cell phone in most of these buildings at all. That's not a good thing, because if I need to get a hold of him I want him to be able to have a signal. Because of this, he's looking into getting a signal booster, or cell phone repeater for their buildings. I think it's a great idea. I'd feel much better knowing I'd be able to get a hold of him whenever needed.