I work in the wireless industry and have good amount of experience with wireless data. The best solution for high speed wireless right now is EVDO data cards - they are fast and in the USA affordable (prices are still high in Canada). Coverage is getting better and better everyday, however the highest data transfer speeds are always going to be where the most people live and work - not where we like to play.
Like Scott mentioned, wireless boosters with a direct wired connection to the phone/data card and an external antenna are one of the best methods for increasing coverage. Cost isn't too prohibitive either - for a few hundred dollars you can have a setup that will last you for years and work with a variety of different phones (as long as they are all of the same techonolgy type like CDMA, GSM or iDEN). Wilson is the vendor of choice - solid reputation and their products are carrier certified (and yes, carriers do shut down people who try to use illegal boosters - and in some cases have them charged under communications laws).
The best way to start is with a simple external antenna and a direct connection to the phone. Get a mag mount Wilson antenna and connector to your phone. See how much additional coverage you get. Next, add in a booster. Test your setup where you like to travel at each step. It may simply be that there is no way to pull in cellular type coverage where you go no matter what type of hardware you have. At that point you need to go towards satelite.
Satelite is a pay to play. You really need to have a good reason to put out the kind of initial cost and usage fees many companies charge. Mobile data connections (surfing on the net while you are moving) gets even more expensive as not only the hardware has to do extensive tracking, but the network needs to be more complex. Over the next 6 months you will see a lot more mobile satelite offerings in North America and with more offerings comes better technology and lower prices.
Steven, for your specific needs and location, I would suggest looking towards Verizon for data card like the Kyocera Passport on one of their unlimited plans.
Hope that helps :wavey:
Pete