NOTE: This article is off-topic: it has nothing to do with privacy. If you are looking for privacy articles, you might want to skip this one. However, it is something that I believe all cell phone users should be aware of. The online app called Zello could save your life. It is also a great way to communicate with groups of people, such as relatives or members of a search-and-rescue organization. I have been using Zello for non-critical communications for a couple of years now and would hate to be without it.
Zello converts your Android or Apple iOS or Blackberry cell phone or your Windows computer into a general-purpose walkie-talkie. It is sort of a high-tech replacement for CB radio except that Zello converts your cell phone into a free 2-way radio with worldwide range. I have used the free Zello app to talk with friends and relatives in North America free of toll charges while I was walking along the streets of Singapore as well as when I was in New Zealand. I have also used it to talk with communications hobbyists in South America and in the Sahara desert while I was driving in my automobile in Florida.
Zello also was recently used in the Houston area, New Orleans, all over Florida, Puerto Rico, and in other Caribbean islands during the recent hurricanes when wired telephones and emergency two-way radio towers (police, fire, ambulances, and others) were destroyed by the hurricanes. Cell towers also were sometimes knocked offline during the hurricanes but usually were the first communications systems to be restored to operation once the winds subsided.
Perhaps the greatest story of all was the use of Zello by the “Cajun Navy” during Hurricane Irma. According to Wikipedia: