Google has added a feature that lets Google Play users top off their credit by simply visiting the Web version of the storefront. The move comes on the heels of the recent introduction of in various retail stores.
Scrolling to the bottom of the Google Play store, you can now click on a link that allows for credit refills in various denominations. It's possible to purchase credit in increments of $5, $10, $15, $25, and $50.As of now, it's only possible to add to your own account, though I suspect we'll see gifting at some point. Also, the new redemption method appears to be limited to the U.S. market only.