How can you possibly even consider going in this direction when there has been so many security flaws discovered in the past week.  So you want to take an inherently flawed system that does not allow for an always encrypted wallet.dat file and allow for a physical device that will be used to make store purchases.  Ok right now do you know how many billions of dollars are already being stolen by credit card skimmers?  But hey its alright because the bank will cover losses to these transactions.  Now you want to take an inherently insecure system that has no bank to protect against fraud and make it also vulnerable to skimmers.  Great idea.  Put an rfid chip in it while your at it so they can do it at a distance.

Why don't we first decide to create a platform for secure transactions as they exist now and worry about applications like this later.  I mean have you seen all the problems people are having with compromised mtgox accounts.  Nothing about bitcoin is secure or reliable right now.  Once we can secure the wallet.dat to be always encrypted and we can provide for a secure way to exchange this currency without worrying about an ewallet that can be compromised then lets talk about taking digital currency into the realm of the physical real world.

What we need is an always encrypted wallet.dat file.  Till this change takes place everything else is vanity of vanities because it means bitcoin will never be taken as a truly secure form of currency.