The official Skyrim map app recently hit the app store, and the good news is it's free—up to a certain point. Pay nothing, and you'll have access to information on the nine major cities, plus a little more. The rest of the content can be unlocked through in-app purchases.
It's not like you're going to use this when you're actually playing, since the game, you know, already has a map. But it is pretty neat once you unlock all the content for $9.99; it's got "every primary location, secondary location, point of interest, world encounter, vendor, trainer, skill book, and unique item across the realm." You can also drop custom map markers and keep track of where you have and haven't been.
All in all this is a totally unnecessary addition to your Skyrim experience; but that doesn't make it unwelcome. Let us know what you think in the comments or on Twitter.