http://itunes.apple.com/us/app/gpslocus/id513792496?ls=1&mt=8 GPSLocus is a gps locus recorder, you can use it to record running, climning mountain, bicycle travel, etc, and check the locus on map. You can export your locus through email, just send it to your friends, if he has also installed this app, he can import your locus file through email and check it on his own iphone. Continued use of GPS running in the background can dramatically decrease battery life.
