The idea is that if someone sends you money via Gmail, you can withdraw it at an ATM rather than waiting for an ACH transfer to your bank account. In fact, I don't think you ever even need a bank account, if you choose to use the card to get at your money.
As is PayPal with their debit card. I wouldn't say this is amazingly new or revolutionary, it's just something you can choose to use if it works with your workflow. Incremental improvement.
