In a sense, it defeats the purpose of an adventure cycling trip to carry around a Brookstone catalog's worth of electronic doohickeys. Part of the thrill with adventure cycling is supposed to be in stripping away the soft, inessential creature comforts of home. That said it probably isn't a bad idea to carry at least a few modern-era conveniences, if only for the sake of safety.
Consider, for instance, the now near-ubiquitous cell phone. This one should be pretty self-explanatory. In addition to the obvious safety benefits of a cell phone, you can find plenty third-party apps that cater to cyclists.
The other smart piece of tech to have is some type of GPS navigation system. Obviously, you don't have to have one, but it will save you time and incalculable frustration if you do. There's a robust debate brewing over whether you should buy a standalone GPS system -- as part of, say, an electronic bike computer -- or simply use the GPS functionality (or specialty bike apps) available for many cell phones. We won't attempt to answer that here, but you should know that each approach has its merits and disadvantages.
Gadgets are great, as long as they work, and they can get you out of some serious binds. They also have drawbacks: they need power, which you'll have to source if your trip lasts more than a couple days (solution: yet another gadget, the portable solar device charger). They add weight and take up space; even the miniscule can make a noticeable difference on a bike, where room and loading are at a premium. Figure out what's essential for you to bring along, and then be ruthless about leaving everything else behind. You can always pick up that electric cuticle scraper at a drug store along the route if you discover you absolutely can't live without it.