As of last week, reports the San Francisco Chronicle,

San Francisco's 23,000 parking meters began accepting prepaid cards this week as part of a pilot program that allows drivers to replace the process of depositing coins with the quick swipe of plastic. […]

Drivers can purchase the cards in $20 and $50 increments at six locations around the city, with more locations to open during the next month. Eventually, the meters will also take Translink cards, which are debit cards that can be used to pay for a BART, Municipal Railway or AC Transit ride.

Small detail: Translink cards are not debit cards in the usual sense, i.e. they don’t draw funds from an ordinary bank account. (Although I suppose it's a matter of degree: you could argue that your Translink card balance, which is centrally tracked and cleared, is tantamount to a special-purpose bank account balance, with the Translink consortium playing the role of the issuing bank.) They are better described as prepaid cards.

The coolest feature of Translink cards is that they allow “contactless” interface: you can pay by waving the card past a sensor rather than swiping or dipping it. Technical details for payment technology geeks here.