Not mention the boarder guard probably wants something that wasn't independently seen and verified by millions of other people.

Bribing a border guard at 3am with no phone signal? You are going to want an analogue proof of value; gold, diamonds etc. 

carlosfandango

I've seen people occasionally speculate about how to do it, but I don't think a viable version is available yet. Eventually, it will have to be developed because there will always be demand for physical in-person transactions.