This is basically an ordinary file upload service using sound instead of sharing QR-codes or public links.
My disappointment is immeasurable and my day is ruined.
EDIT: My spidey sense was tingling when a 6mb file was transferred "via sound" in seconds. That would've been pretty incredible.
It also teaches you just how insane the speeds we have today are.
I wanted to store a gpg key offline by engraving it in metal. A reasonably sized one would taken six of the largest 177x177 plates to record.
The best solution I came up with was to use metallic punched tape of some description.
The practical limit was 3KiB for the qr code and there was some metadata in the key I didn't want to lose. I can't remember if it was the private or public key that was giving me the most trouble. But the idea of just having something to point your phone at on a wall and read a signed message from me wasn't practical.
I'm experimenting for fun on this side: https://github.com/dtonon/papiro
> 0–9, A–Z (upper-case only), space, $, %, *, +, -, ., /, :
and so we miss the lowercase [a-z]. Therefore we need to use the 2953 bytes binary option.
Points of difference: I was using a leading metadata frame with filename and total number of frames etc, and the receiving device were ACK'ing frame decodes with its own QR codes. Still, wow.