In the 2014 winter/spring term just ended, I took a seminar in which we read Livy's account, in books 31-40 of the Ab urbe condita, of how, with barely a pause after her defeat of Hannibal in North Africa, Rome gained an irreversible foothold in Greece and Asia Minor by successively defeating King Philip II of Macedon and King Antiochus III the Great of the Seleucid kingdom. You couldn't do justice to this subject without a good atlas, and such an atlas would be the Barrington Atlas of the Greek and Roman World, published by the Princeton University Press in 2000. The really good news, though, and the reason for this post, is that last year Princeton recreated the 101 full-color maps of this atlas as a navigable app for the iPad ($19.99 from the iTunes store, iPad2 required).
The app has several ways of finding a location, including a Gazetteer with over 20,000 locations, corresponding to the separate volume of Indices in the printed version. One feature I found useful during my class was the ability to create Favorites from among these locations, which I did for major battle sites such as "Thermopylae" and "Cynoscephalae." The most obvious distinguishing feature of the app is the ability to zoom in and out within a map. If I search the Gazetteer for "Chalcis," for example, I find it listed for three separate maps, and if I select the entry for map #55 ("Thessalia-Boeotia"), it takes me to that map and then automatically zooms in to Chalcis.
If you have an iPad, I highly recommend the app; the maps are great, and you can have them wherever you go. The app works off the same database of locations, geographical features, historical eras, etc., as the printed version. It's true, you can easily imagine other features for a digitized atlas like this, some requiring an enhanced database, some more sophisticated development, and you should read Chakwin's review on the iTunes site, titled "An excellent book - not well translated into software." But for me, I already love it in its current manifestation.