Encoding entire payment requests into qrcodes is definitely not the way to go. They can already be large when signed and we're just at the start of adding features.

Finishing off and standardising the bluetooth support is the way to go (r=bt:mac). Andreas' app already has some support for this I believe, so Alex you could prototype with that, but we need to:

1) Add an encryption/auth layer on top, because it runs over RFCOMM sockets. The authentication would require proof of owning the Bitcoin key that's in the address part of the URI (which is needed for backwards compat anyway).

2) Write a BIP for it and make sure it's interoperable

For the auth layer we could either use SSL and then just ignore the server certificate and require signing of the session public key with the Bitcoin key, which should be easy to code up but is rather heavy on the air, or roll a custom lightweight thing where we just do a basic ECDH, with the servers key being the same as the address key. But rolling such protocols is subtle and I guess it'd need to be reviewed by people familiar with such things.

This feels like a good opportunity to grow the community - perhaps we can find a volunteer in the forums who enjoys crypto.