Worried about your friends in the path of hurricane Irene? Zello was among the key tools used by rescuers to help victims of Hurricane Harvey in Houston. The go-to app Zello, is a walkie-talkie app where you can push a button to talk to anyone through a cellular or Wi-Fi connection. My son lives in Tampa and just told me about this, so I can be in touch and not worry. It is the most popular free app on both Android and iOS app stores at the moment. With over 600,000 new users in 3 days, there must be something to this.