It ain't cheap, but it's possible: Popular Science shows us how to install a solar-powered work-from-anywhere Wifi hotspot in your backpack, so you can check email during a leisurely country hike.
Using the previously-mentioned Voltaic solar-panel backpack, WiFi-anywhere EV-DO equipment and some elbow grease, and you can be Flickr'ing photos of nature on the wilderness trail at up to 700 kilobits per second via the wireless hotspot on your back.
Be Your Own Hotspot [Popular Science]