My friend posted this up on facebook and although this is for Android, pretty sure there would also be something out there for Iphones as well.
It's an eventing app designed to make mapping cross country courses easier using GPS technology. Apparently you shouldn't have to measure your course anymore so you can just concentrate on walking it and the app does it all for you, working out minute markers from the optimum time you enter.
I haven't used this, I just thought that it would be worth sharing. It has good reviews and 4.5/5 stars, so they must be doing something right!