We all know about the various running apps that we can take advantage of, such as RunKeeper, MapMyRun, and MyFitnessPal (more apps in the running app Hive Five). Most of them will track your time, route, and distance in real-time using your phone's GPS. However, another good use for these apps is tracking the sightseeing you do when you're in another city.
If you plan on doing a lot of walking to get around to all of the points of interest while touring a city or national park, it's fun to boot up your favorite fitness app and track how far you've walked and even where you've walked (since most of these apps also provide maps of the routes you went on). Plus, you could technically count that as exercise and enter it into the app to meet your weekly fitness goals, so you'd be killing two birds with one stone!
Of course, there's also Google's My Tracks, which is more focused on activities like this, but it's only available for Android, so if you can't get My Tracks on your phone, a fitness app is the next best (or even better) thing.