The pertinent sections:

In many cities, riders have to use a specific transit card for their commute. Working with transit agencies and other partners, Google Wallet makes it easy for riders in some cities to purchase and store your transit pass directly on your phone. We recently started rolling this out for transit riders in Madrid. And starting soon, people in Seattle and the Puget Sound Region will be able to add their ORCA transit cards to Google Wallet.

This is not only a convenient option for people looking to store their everyday essentials on their phone, but also a way to get your new transit card instantly, easily reload the card and set up auto-load.You can also view your real-time transit card balance and transaction history, all from the convenience of your mobile phone. This is helpful for keeping track of your spending and making sure you always have enough fare on your card.

Looks to work with android watches too.