Mike: Why require EV certificates? They are VERY expensive, and pretty unavailable for those in countries that does not have any available EV certified CA since the EV certification requires in-person validation.
They wouldn't be required, it'd be nice to support them though.
That'd mainly be for online transactions that are sent to your phone for processing. Maybe I should remove that section given the page is about in-person transactions. Consider if you are shopping online from a computer with a virus on it. You can click on addresses or links to send the address to your phone, which then asks for confirmation. Your wallet is on your phone so the virus can't spend your coins directly. However it can rewrite addresses you see on the page to point at the hackers wallet instead of the merchants. If the addresses can be signed the virus can't do that without making the verified business name disappear.
A simple approach could be a color image created from the bitcoin adress. The color image is posted at the cash register in a tamper resistant fashion, and you simple check that the image that comes up on your phone just looks like the image at the cash register.
Yeah, like identicons.
But the problem is that not everyone has smartphones
They will do soon! Android alone is selling at the rate of several million phones a week, vs exactly zero for custom BitCoin card readers.
I have to leave my phone in the locker outside the store for example, before going in.
OK, but that sounds like a bizarre problem unique to Sweden or even that particular chain of stores. I mean most shops solve that problem with CCTV or anti-theft tags. I've never encountered stores that require you to place phones inside lockers before going in, it must be an absolute business killer.
Anyway, I think the key point here is that nobody today has BitCoin smartcards or readers and there's no way to solve that, short of a large business coming in and doing the necessary development work, selling the cards, building the readers etc. Not going to happen.
Smartphones are just as good, except they are already being deployed en-masse. Nobody has to do anything beyond writing some software.