The problem with a game specific card is the money you have to spend on distribution, store placement, not to mention the cut your resellers take from each sale. Then theres the effort needed to get stores to carry them.... that more then anything else is massively difficult when your not affiliated with someone with ties to the right distributors.

In order to make money this way, you'd need to sell in volume... and I'm not sure if the player base is large enough to even warrant it.

I live in England and all my CE purchases have come up at the checkout in pounds sterling. Typically I pay with phone credit - I almost always buy phone credit with cash or from bank machines, so there's not a card directly associated with it, but to be honest it's mostly for the sake of convenience (my credit card is for the direst emergencies only and is not usually on my person).

If your local currency isn't showing up on checkout, you can always use conversion sites like XE.com to check the exchange rate before you buy. Hell, I think you can do it in Google even.

Its essentially using the phone payment as a pre-paid gift card. Its common service in major countries (except the US... we're pretty archaic when it comes to institutions), where phones integrate better into every electronic system, and is slowly becoming the new ID system.