That and, what's the price difference between a USB card reader + supercard with screen and such vs the cost of the cheapest BTC runnable smartphone?
I imagine the "supercards" are less than $20. The point is that once you have a display and keypad, you don't need a reader. So the cost is similar.
you could just input the price they display to you on your card, enter your pin, then hit send. The card signs a tx with only that exact value so they can't change the price after you begin entering your pin. It could be doable but it seems a bit complicated imo.
No, there's no need to manually enter the transaction amount. Transactions can be sent over the wire. This is irrelevant.
I was talking more about security from merchant overcharging, and for that matter, since BTC is spent by referring to previous txOuts, you'd have to load all the txOuts onto your card, or trust the merchant to construct a tx with the proper amounts that pays you the proper change. If the merchant is using a USB smart-card reader, they would have even more room for messing with clients since there are no software restrictions on a general computer as opposed to a specialized card payment unit.
I agree, it would be nice, but you'll have to seed the market. Markets can be big or small as in mass marketing or niche market. They can be high margin or they can generate losses. Markets in the strategic design sense is separate from profits. People can seek profitable markets are narrow their definition to make the market more profitable (i.e., exclude poorer people) A market is just a collection of people who you believe will benefit from your good or service. For programmers it's like a collection of objects, where objects are always human being.
It is important to be able to visualize the participants you are looking to serve. It is difficult to design a system for a foreign market w/out understanding their infrastructure. In one design I had to go back to flip phones (SMS) and a middle office because that was the only reliable technology people in that market had access to on a consistent basis. When defining a market segment I look for what is the most accessible, low-cost technology at the POS for both customer and merchant. So in the case of Greece solutions may well look more like M-Pesa (9 million people in 3 years! A top down authoritarian model. They're being studied at all the top B-schools now) or the mobile solution in Ghana (open source with equal rights to participation for all consumers and all telcos) Don't assume that b/c those economies are lesser developed that they haven't found a way to exchange value without using the debit and credit card networks, b/c they have an in that sense they are years ahead of the US (ironic isn't it?) Mass market access to mobile payment, elite only access to Visa/MC.
Can these solutions be fully automated? Yes. As for the cost of service, you are essentially getting the Telcos to dump data into a middle office for processing and then you need to be able to send replies to both the merchant and their customer. These Telcos modules are now a commodity product (See BOKU) I can find out how much it costs here in the US if you'd like that reference point. But I don't see why you can't build your own, I mean it's just bits and bytes across a wire like all e-payments. Can't you grab the data from an email client and process it? Yes the run rate could be higher than that of a cobbled together smart card system, (# of SMS messages per month) on the other hand once you write the customer/merchant facing app and automate the middle office (just a big data base with a few rules) you don't have to spend a whole lot of time installing hardware and the merchants won't have to buy any new systems or devices. Oh and for BTCs system users would also need cloud-based wallet services.
Well, I can see that M-Pesa works. Theoretically BTC should work under similar conditions. However, I don't know anything about cloud-based services, and I don't even own a smart phone =\. Where possible, QR codes printed on a receipt are probably the easiest route, requiring only an internet connection to validate, but again that depends on what hardware is available for clients as well as what is typically available for merchants. The only way to find that out is to visit Greece and see what it's like. If smart phones are common and merchants can easily get an internet connected computer, then a flip phone service would only be needed to make it available to the stragglers. If the best anyone can afford is a flip phone, then you're pretty much stuck with centralization, which is a Very Bad Thing in a confiscation-sensitive environment. Also possibly relevant are the fees incurred by said service, although really it shouldn't be more than current banking fees.
Security is another big question, I think. What happens if someone steals your phone? How do you enter a pin or something without your phone recording it? Etc etc.