I haven't used the program referred to in that link, but I have used Motion X GPS on my iPhone and it is terrific. No problem with crashes. You have to download the area maps where you will be if you will be out of cell contact, but the download is quick and intuitive.

Battery use is an issue, but there are lots of portable power supplies.

The display and map detail is far superior to what I get on my Garmin 60. I did a side by side comparison of the app and my Garmin and accuracy was comparable.