The big trick would be doing it self-supported with no sag wagon, carrying your camping gear. One of the Surly guys actually did some short self-supported trips on his unicycle - try searching the Surly blog at www.surlybikes.com
. I just learned how to ride a unicycle and my biggest concern is how much pressure you put between your legs. The better I get, the less of an issue it is, but considering that you don't have any weight on your hands there is no way that it isn't worse than riding a bike. One other thing about unicycling long distance is that a 36" wheel is the way to go since that is effectively your gearing. A 26 or 700c wheel is a bit slow for long distances at a 1 to 1 gear ratio...