Depends on what you mean by "working". The TenX card "works" in that it successfully converts cryptos to fiat but there are some potentially serious legal issues in the US and other countries. Using TenX as an example - you are not actually buying anything with cryptos from a vendor - you are converting cryptos to fiat and then giving fiat to the vendor. In the US if you convert cryptos to fiat you are legally obliged to pay capital gains tax, at rate that can vary wildly depending on how long you have held the cryptocurrency. So for these "crypto debit " cards to be feasible in the US they need to either exchange only cryptos for services/products, or convert cryptos to fiat - collect or at least calculate capital gains owed - then give fiat to the vendor. Very dicey. I love the idea of using cryptos to buy stuff in the real world, but the legal grey areas are rather large at the moment.