Verizon anywhere wireless cards? Or any ISP anywhere wireless cards?

What I am asking about is if anyone knows anything about a card that Verizon (or any ISP) supposedly has that you can get internet wherever there is a cellphone signal. I am a courier in the DC area and I take my laptop on the road with me and it would be nice to be nearly anywhere in my car and can get internet access. It does not have to be Verizon, I am searching for any ISP that can provide this service. It is just I have heard the most about Verizon. How much does such a service cost month to month? Where can I get a card? And can I still be connected to my home network with such a card? Thank...