Sending files purely via sound

This project is exactly what I was looking for except the limitation for message length and the transfer of files. I suggest the possibility of sending files purely over sound, without any additional type of connection. This could be beneficial in environment without any internet connection and for secure transfer of private data (such as private keys) without any need of LAN network or any internet at all.

Not sure how difficult would be implement splicing data into 140 chars and then sending initial message with number of messages to be transmitted and then checksum in ending message. Or using less then 140 chars plus initial integer for the number of messages. Then receiver would request these messages to be sent again in case of transmission failure.

Hope this makes sense.