Device-to-device audio communication (think QR codes, but made out of sound) seems very underrated. Much better UX than QR codes or NFC because you don't have to worry about putting your phone in the exactly right place or pointing it in the right direction.

Anyone here with more detailed takes on this?

I feel like there could be a lot of crypto wallet applications.

Perhaps is interesting for some use cases like blind people using sound QR in desktop apps but very difficult to verify the authentic sound source. We need also QR stickers to bar order 🤣