Edit- and I mean different from Coin in a use case kind of way. I realize that Coin does stuff with the magnetic strip directly whereas this is just another card that is linked on the net to all of your other cards.
In any case, big whoop.
I'm leaving the original below anyway...
I believe it is linked. The idea is that you'll tell the app you want to pay with your Amex. You hand the Google Wallet Card to the retailer/waiter/etc and when they run the card it will be piggy-back-charged to your Amex by Google.
The difference to Coin is the switching to your "real" card is done in the datacenter not on the card itself via the mag strip.
And when the world evolves to contactless payments as the norm, you've already been trained to use the Google Wallet App (which supports that), whereas Coin will be obsolete.
Google is playing the long game.
> The Google Wallet Card is funded by your Wallet Balance. Money is added to your Wallet Balance either by someone sending you money via Wallet or Gmail or by adding it yourself from a linked bank account or from a credit or debit card. The card has no fees to order and activate. There are no annual or monthly fees for the Google Wallet Card.