Something attached to the main computer, but with its own firmware/controls is still far better than having no device at all, and relying on external code for verification. Would a discrete box separate from everything else be better (independent of mobile phones as well)? Sure. But a great step that would be progress compared to the current status quo is what the other poster describes, with logic and chip verification running on a device attached to the device or computer with which you wish to pay.
Something attached to the main computer, but with its own firmware/controls is still far better than having no device at all, and relying on external code for verification. Would a discrete box separate from everything else be better (independent of mobile phones as well)? Sure. But a great step that would be progress compared to the current status quo is what the other poster describes, with logic and chip verification running on a device attached to the device or computer with which you wish to pay.