From what I read about open dime you do a one way physical action which changes the circuitry to reveal the private key when you plug it in. I’m not sure if you can validate the amount on the key before hand but once that seal is broken you are saying you’re the one to spend it on-chain as at that point someone else could have the private key and already spent it. Additionally you really have to know how this device works to accept it as payment cause otherwise someone could trick you by giving you the unsealed portion without you realizing the implication and you have to know how to safely verify it. With cash you only need to know how to detect counterfeit notes.

The same issues with opendime apply to satscard - cash can be transferred thousands or tens of thousands of times and doesn’t carry any extra cost and can be trivially broken up into smaller transactions. This thing requires gas fees to transfer onto and off the card + the cost of the card itself + limited number of transfers if you want to change the amount.

These devices are clearly meant more for long term cold storage using physical security to avoid losing the key and not as a way to replace cash transactions. Totally different applications even though cash also can be intrinsically used as long term cold storage (just more complicated physically)