s/gold/bitcoin/ = WIN
I just realized that to some degree we today already have a bitcoin-denominated debit card.
I can leave $0 in my PayPal account and then just before making a purchase I can use CoinCard to add funds to my PayPal account using bitcoins. I can then use my PayPal debit card to complete a purchase.
Of course, this isn't efficient either timewise or when considering fees. CoinCard's fee for doing that conversion is 3%, or $1 + 1% for transactions $50 or more, and then getting funds back into bitcoins isn't the easiest or cheapest either.
However Bitcoin truly is leading the charge. This combination might possibly qualify as the first commodity-denominated debit card option available to us.