I think that there’s a good argument for something akin to a dedicated smartphone, probably smaller and with less fancy electronics, that has an internal keystore and is used as a highly-secure device for things like authentication.

Like, if I want to buy something on Amazon, I plug my “authentication tablet” into my computer’s USB port and the computer just acts as a proxy for the information required for the transaction; I get a pop-up with the details of the transaction, need to authorize it on that “authentication tablet”.

Something like a YubiKey isn’t, I think, really sufficient, because you don’t have a trusted display and trusted controls to authenticate.

As things are today, general-purpose computers just are too easy to compromise for me to be super-happy about putting really valuable stuff that someone might want to target. They have a big attack surface, and they permit a lot of end-user customization. I don’t want to make my general-purpose computer locked down to the point where I can’t customize it, because that has value. I just want to put really critical things somewhere other than on a general-purpose computer.