YES - I realize the private key would need to be shielded for it to be used for more than one transaction, but the low tech way would be a simple sealed windowed envelope or a better way would be like a scratch off or fold and glue paper. Cassius coins was sealed, so you just need a way to tamper proof the private key while allowing the public key to be verified for the amount.

I think the concept is sound and it expands the audience to people beyond the tech realm.

Cheers!