You mean like the debit card in my wallet from CAVirtex?
Ok, I admit it won't do the automatic conversion...but this is the first iteration.
Next step according to them is exactly what you want to do, convert $ to btc on the fly, and pay for items in local currency.
What I have to do right now is sell some coins and transfer the amount to the debit card.
But hey...the other day I bought groceries with my CAVirtex debit card using funds I received when I sold a small amount of bitcoins via the interac network.
It's getting there!
Thanks for bringing this to my attention, Didn't know about CAVirtex. Sounds awesome.