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.