Quick question... Why cannot cellular frequency be used without cellular towers, in peer-to-peer style? Like: you send SMS, it's regularly broadcasted to all phones within reach, they re-broadcast it regularly, it's received by the end recipient, it replies instantaneously with "Message X received, stop shouting", they broadcast messages "Message X received by the end recipient, stop shouting" to everybody, when sender receives this message, he knows that message is received and stops sending it. It has large potential for an avalanche, but utilizes no costly cellular towers. If you send/receive messages rarely and place calls once in a month, the P2P network will be underused. It works better when the density of phones is high enough to be reliable and low enough to prevent an avalanche.