On several dive expeditions I’ve taken, particularly off the coast of Catalina island in Southern California, I’ve had the opportunity to use my Cradlepoint MBR1000 to connect to my work email and to manage the health of my websites. It is a simple router that I can just use with my Verizon USB 3G modem. It takes the 3G signal coming off of the nearby cell towers and converts it into a wifi signal that me and my buddies can use.
There are several mobile broadband routers and not all of them are right for everyone. Some take different types of modems, others work with different cell carriers. I’d recommend you read this article about the mbr1000.