If it requires an NFC connection to chech the current balance, why the banknote is different from a mobile wallet? It's only that if you hand it over, it does not require a transaction to wait for?
The fact that the private key always remains secret in the chip means that they seem to be made for handing them over like you would a bank note.
They aren't really notes but cards:
The problem I see with that is that they are selling them for $199 for a pack of 10 unloaded cards. So who is going to want to hand over a device worth $20 when they spend $100?
They look like a pretty cool hardware wallet but I couldn't consider them bank notes.