Right now I'm fascinated by this prepaid Lightning card. The QR code on the back recharges the card with lightning network.

The embedded RFC circuit holds the private key in conjunction with the pin code.

I wish I could have gotten these as presents instead of Bitcoin wallet keys!

Currently I think only the Tiankii machine reads the cards like a normal debit card.

There is a block height that I can look up, but I don't understand exactly how this works yet and what limit of money can be stored on it and for how long.

I also wonder if my phone's NFC reader could be used to bread this card.