Serval Project is an autonomous mobile network for non coverage areas, it requires no mobile phone company to operate, using Wifi enabled mobile phones transmit data in P2P mode, ideal for deployment in disaster areas where mobile phone towers have been destroyed and remote places where mobile phone signal can not reach.
The software called Distributed Numbering Architecture (‘DNA’) turns an Android phone into an independent network router broadcasting and managing calls in mesh P2P mode. To enjoy adhoc wireless networking you will have to root your phone invalidating its warranty, if you choose not to root your mobile phone you can still use it for free P2P calls with people connected to the same Access Point but you won’t be able to transmit data like SMS messages, called MeshMS, and share files.
The Serval Batphone software will guide through installation using a configuration wizard, the settings allow you to make a call through the Serval network, suspend services to allow your phone to operate as normal with a mobile phone company providing coverage, and reset your phone number, which can contain from 5 to 32 digits, numbers starting with 11 are reserved for emergency lines. If something does not work you can troubleshoot problems by going to the Wifi settings changing the SSID, frequency channel or router implementation, advanced users can create a new mesh on a different subnet changing the network address.
Serval makes use of SipDroid, an open source free VoIP client for Android, options found on SipDroid can be found in Serval too.
Although the initial idea of this project is to provide mobile phone coverage to extreme poverty and remote zone areas, I can envision the utility of this network by a group of acute paranoid people concerned about mobile phone companies keeping logs of their calls or fed up paying high fees, but every single node in the network would have to be trusted for this since they route the calls, probably not feasible with you have a large number of devices and impersonation is fairly trivial since there is no central authority allocating phone numbers, solutions to these problems could come in the form of call encryption and requiring a verbal identification password when the call is established.
Currently still in development, it has been successfully tested by the developers in the Australian outback to make P2P mobile phone calls covering 1 square kilometer, future features include filesharing with people who are not reachable at the moment and a version for Apple iOS.