I'm not sure it's worth going through all this, risking small transactions, getting telephone calls, relying on a 3rd party site,
That's fine, no one is going to force you to. But some people will find it useful.
Someone mentioned that you can hack a $20 mp3 player and install your own software. It's already got a display, input device and usb plug.
Any chance you could find that reference? I would love to see it, but searching for "hackable mp3 player" doesn't turn up the sorts of things I'm looking for.
By the way, I am actively working on the hardware device route. I know what capabilities it is going to need, and what the communication protocol is going to look like, but I haven't yet found a hardware platform that is both simple to develop on and capable of doing the crypto.