I've made a PCB and I've got some bare bones working code.  I will get pictures of the PCB up shortly (my first one!).  The github link has been added.

So I've shown a proof-of-concept of sending a "file" one way over the serial port (what's actually happening is parsing the file, sending what's being parsed over serial port, then creating a new file and storing what's sent into a new file on receiver side).

What's really needed now is better parsing of the SD card (to get all files on the card) and a good forward error correction (FEC) implementation.  To really make this idea good is going to take a lot of work, if someone can do it please show me.