Starbucks (for payments) and the airlines (for boarding passes) have done pretty well with barcode scanners. It requires hardware only on the merchant side than most merchants already have in one form or another.
Not quite. Starbucks uses its own pre-paid system that does use a plastic card, but one without any major network's logo on it. It's just store credit.
And in America (I believe - last I heard it was rolled out in some American cities but not others, nothing here in the UK) the iPhone/Android/Blackberry(?) apps let you manage your account balance, and you hold up your phone for the cashier to scan the barcode off your screen.