They are apparently working on three mechanisms, one being through a cell phone, and two being secret.
Is there anyone out there doing a cell phone transfer mechanism? I can think of two possibilites for making this, one being more viable, and the other one being more in line with the ideology of bitcoin.
The first one is that you interface with (or create an) exchange like mtgox. Payments would be instant but there would be a single point of failure.
That other is that you run bitcoind, either on your phone or your home computer. Shopkeepers could potentially accept payment after just one block, since a low but existant scam rate could probably be tolerated.
For really high value items it would probably be too insecure, and waiting would be too slow.