If you live in the south or the Great Plains, you know the feeling of going to bed without knowing if your house will be there in the morning. Tornado is the latest in the American Red Cross's series of disaster relief apps, and since tornadoes are by their very nature sudden and unpredictable, it's a welcome addition to the Play Store. The app ties into the National Oceanic and Atmospheric Administration's alert system, and emits an alarm when your area (or any area you designate) receives a tornado warning. There's also an all-clear signal when the danger has passed.
Like the previous disaster relief apps, there's also a handy "I'm Safe" button that will send a pre-recorded message to your friends and family, plus a constantly-updated list of local shelters.