The only-ten-minutes timeframe is necessary as the invaders (a domestic militia group gone rogue, not foreign invaders) have set up a false emergency elsewhere in order to lure most law enforcement out of the town. The remaining few cops (my heroes) obviously call for help as soon as they know what's going on, but there isn't really time for help to arrive. So the townsfolk mobilize.
The system of P2P developed separately from the way it was used in Iran and in the Arab Spring. Cell phones and the Internet access is different in other countries than in the Western World. In countries where the government tries to censor the Net and control information, a need arises where people find ways around it. And in countries with unreliable infrastructure, P2P was sort of a natural spinoff of that need. Don't hold me to this explanation, it's my current lay person understanding of how it works. Your phone is broadcasting and receiving data to and from the cell tower. All you need to do to have it send and receive between phones is change the identifier you are sending and receiving from and to, that locks you out of other systems. So you have a particular phone/wifi service and you make a call or use data, your cell phone is communicating between your IP address and the company you pay. But different companies use the same cell towers. Your SIM card controls the gate. Nothing inherent in the phone mandates it only talk to the tower. As for the story as @BayView is describing it, it wouldn't be unusual to have a community that was using P2P communication. You might need to lay some sort of groundwork to fit it in the story, but enough people know what P2P is that it would be credible to use cell phones like a broadcast system. You notify 2 people, each passes the message on to 2 more, and so on. It doesn't take long to get such a message amplified to reach a large group of people. In my book people use it to bypass the Grid (Internet) where everything one communicates becomes part of the accessible database.
Zello is a app that lets your phone function just like a radio/walkie-talkie. One person can reach a large group at the touch of a button. Larger groups require primium version and there is an upper limit but if you simply want to expand that concept its a far stretch from making something up entirely. It's completely plausible.
I didn't read all the posts in this thread admittedly, so I apologize if someone has already suggested this. First, I really liked the app idea, even though you said you'd feel ripped off as a reader. I think not necessarily so, because perhaps there is an app out there already that might be like that, and it's not unbelievable to assume that there might be an app in the near future invented that does that. A different cool idea that might not fit with your story is if you had some genius character capable of quickly creating an app like that. I don't think that would be completely unbelievable as long as the character had those capabilities. Also, I do know of an app called GroupMe where you sent text messages to the entire group and everyone gets the message. It's not voice it's text but it might be the next best thing, some kind of group chat. Also, in China they use an app called WeChat, and one of its capabilities is that you can send a "voice text" where you hold a button and speak into the phone and then the person receives it and plays the short voice message you recorded. Both of these apps might have potential in your scenario, or some combination of the two.
How many people need to have instant communication after the take over starts exactly? There a lot of truck drivers passing through small towns. The trucks have CB communicators. They are normally attached to the truck though, but with today's technology, are their mobile hand-held CB's that truck drivers use? Also, would the CB communications be targeted logically as well?
If there were hand-held CBs, that'd work fine - assuming there were enough of them! (I'd think it would be best if everyone had a device, but even if just some did that'd be okay...)
We have a neighborhood earthquake plan (promoted by the fire department) where people are identified with various tasks: shut off the gas, babysit pets and kids if parents can't get back, search and rescue, first aid and so on. Neighbors with CBs are identified and volunteered to be main sources of communication if the radio/TV stations weren't broadcasting. But I still think the cell phone aps make more sense if the story takes place in contemporary times.
I've already written the scene (went with minimal communication because it wasn't really crucial to the story that they be able to communicate - it's SUPPOSED to be chaotic, so I mostly just wanted to be sure I wasn't missing something totally obvious). But I'm still appreciating the answers - never know when this situation will come up again, and I'll be better prepared that time!
