The iPhone App That Could Save Your Life

127 Hours, ultimately resulted from the fact that no one knew where he was, leaving little chance he'd be found before dying of exposure.

Since then, several GPS-based emergency location systems such as SPOT Satellite Messenger and the Ralston-approved ACR SARLink 406 GPS have come to market, some of them highly reliable, with long battery life and satellite communication that doesn't rely on cell phone reception. Once it's activated, you're pretty much assured of being found.

But what if you forget that, too?

One backup, a 99-cent iPhone app called Yodel, could be the difference—literally—between life and death. Yodel automates the process of checking in with friends and family by email or text. With a few clicks, they will receive your trip plans, including estimated return time. As you travel, you can mark waypoints so that your contacts can track your progress (or just so you can show off the awesome things you're doing). At the time of your scheduled return, the app sends you a personal message to remind you to get in touch with your contacts about your safe return (by pressing a single button) or any changes in itinerary. And, if there's any trouble, Yodel's SOS function can send an emergency message with your GPS coordinates to your network and autodial 911 or another designated emergency contact.

It's a solid system, but there is one major drawback. The app is dependent on iPhones, which have limited battery life, aren't waterproof and tend to have spotty coverage in the backcountry. For these reasons, it's probably wise to use Yodel for short trips, or in conjunction with a GPS-location system for backcountry use.