Really: it alerts your emergency contacts when you don't respond to texts.
Have too many Law & Order marathons convinced you that, at any given time, you're probably about to be murdered? Me too. Fortunately for us (and our loved ones), there's Kitestring. When you're on an trip, you can set up Kitestring to send you a text message at a specified time. If you don't check in (by responding to the SMS or checking in on the mobile-compatible site) within a few minutes, Kitestring will notify your emergency contacts.
Here's the message your contacts receive if you "go dark."
In one sense, the app's applications (see what I did there?) are clear. Kitestring could prove a priceless safety net for anyone who travels alone, or anywhere they don't feel entirely comfortable. That said, this is bonkers. Yes, if you're running late, it's possible to extend your trip on the go — but knowing me, there is no way I wouldn't have misplaced my phone, allowed its battery to run out, or simply decided to take a nine-hour nap in the middle of the day.
You can sign up for Kitestring for free, if you don't mind your mom frantically calling every hospital in the tristate area when you accidentally set your iPhone on Do Not Disturb.