Spyglass (U.S. $3.99 on sale) is a really complete GPS toolkit for people spending time outdoors or doing off-road navigation. Features are numerous; among them are a heads-up display, a high quality compass with map overlays, a gyrocompass, speedometer, altimeter, astronomical object finder, a sextant, inclinometer, and angular calculator and more.
The app makes use of every sensor in your iOS device in a simple to use package. Waypoints can be saved and navigated to by following a simple pointer. Spyglass can track multiple destinations at the same time, and display distances, direction, azimuth, elevation and ETA. A rangefinder measures distances to distant objects. The app can utilize your camera to provide photos with data overlays.
Hikers and others going off-road will really be excited about this app. It has a myriad of functions all wrapped up in one place.
I tried the app and found it useful, even in urban life. You won't get the most from the app without reading the instructions, and there are some nice videos available as well. This isn't a typical navigation app with streets and hamburger joints; it's a sophisticated tool for finding your way when there are no roads or obvious checkpoints.
It's customizable, even to the colors of the displays and the filters over your live picture -- for use at night, for example.
I do a lot of landscape photography that involves some hiking and car locating. Spyglass was a trustworthy companion for that endeavor, including estimating my altitude and distance to destinations. Getting back to my car was easy, just a matter of following an on-screen pointer.
If Spyglass interests you, there are online videos and a manual you can check before you buy. Spyglass needs iOS 6.1 or later, it's universal and therefore friendly with all iOS hardware, and it's optimized for the iPhone 5.