Ever since the introduction of the iPhone 3G, Apple has allowed your photos to be geotagged, either by shooting with Apple's default camera app, or with 3rd party apps that supported geotagging.
Since the introduction of iOS 6, metadata has also been recorded with each shot, however there is another unknown little feature, and that is, with each shot taking with Apple's default camera app, not only is your location recorded, but the direction you were facing.
This only works with the iPhones default camera app, and not all apps or services can show this data, however PhotoMeta for the iPad [App Store Link], from Galarina can and does show this data.
Source: This tip came via PhotoMeta's developer, Chris Cornelis. Chris has written his own blog post, which can be found here, about his app and the photo direction feature.