Look into MotionX GPS. It's an excellent full featured back-country (no driving directions) GPS app.
One of its many features is location sharing via email. You set the schedule (say once an hour) and the recipient email(s). You can also enable/disable it at will. It will send an email on schedule with a clickable link showing your exact lat/long. The back-country use for this is if you don't return from your trek, someone will have your last location.
It will also record tracks. You can then upload tracks to the net, load into Google Earth (this is cool for skiing), upload to facebook, etc.
Remember that if you run ANY GPS app in the background, it can eat through your battery quickly.
http://gps.motionx.com/iphone/overview/