Depending on where you are, cell phone coverage could be between great to totally nonexistent. The mobile apps are built to be able to handle intermittent cell phone coverage. You can see yourself on a ski resort's map at all times, as well as see your own statistics. When you get in a cell phone coverage area the app sends the latest information to my servers, and receives information about your friends. You might get some stale information, but that's still better than nothing. And of course, if you're in a ski resort with great cell phone coverage, your friends location is fresh most of the time.