Barcodes have been around for a while. Will retailers need to add anything to support Passbook?

Schwan: They may need to replace a one-dimensional scanner with a new two-dimensional scanner that tends to read reflective screens well. A lot of big retailers have already made that investment and have two-dimensional barcode scanners.

But retailers still need to iron out their processes to support paying redemptions with phones, everything from getting two-dimensional scanners at all the registers to facilitating business processes. It's one thing to get up to the counter, and the retailer doesn't really know how to redeem your coupon on your phone, verses a retailer who can't accept the payment. The former is a little more of a challenge than the latter.

The Passbook approach allows [retailers] to work out the kinks before full-blown mobile payments and mobile wallets are exposed.

What needs to happen for Apple to take Passbook to the next step?