If you have a need for coordination, within the city, with a group of people, then it may turn out that phones are not as effective as you previously thought. The catch is that you will not be able to quickly communicate information to several people on the phone simply because each call takes quite a long time, which is usually not essential for you. Plus, telephone channels are very poorly protected simply from the point of view of security and control by people who should not be trusted.
But, as always, if you and your friends have smartphones and Internet access, then you will be able to transmit information very, very quickly. And safe. We'll tell you how.
The Zello service helps to establish instant voice communication, mobile applications of which are available for literally any type of smartphones: iPhone, Android, Windows Phone, and even Blackberry. Zello works like a walkie-talkie, and works incredibly nimbly. Even on the low-speed EDGE/GPRS Internet (tested personally).
It is worth saying that Zello takes great care of the phone's battery, and the smartphone, with very active use (tested on iPhone 5s), will live with it for 6 or more hours on an EDGE connection (it is less energy-intensive than 3G or 4G).
For coordinators and just "sofa warriors", a Windows version of Zello is available, which allows you to broadcast and listen to communication channels to which you have access.
The good news is that Zello is completely free to use. So, you can be in touch with friends and like-minded people no worse than "specialists" equipped with expensive rattles. If you are serious about security and independence from the central server Zello.com , then a solution is available for you in which you can configure work through your own server in any IP network - the solution is called Push—to-Work. It is free for groups of up to 5 people. If there are more of you, then you need to pay. For example, your own group for 100 people will cost $500 per month, or $4,800 per year.
But, if you use a free application on the Zello network, then everything will be free. We have tested the operation of the network within the district with 650 participants - flawlessly!
Zello Blackberry and Windows PC
Zello