Amazon’s in-app purchasing is now available to Android and Kindle Fire developers, the online retail and publishing giant announced today.

In practical terms, this means that anyone will now be able to offer digital content for purchase within apps, including subscriptions, but also one-off transactions for “in-game currency, expansion packs, upgrades, and magazine issues,” Amazon explains.

As you can imagine, this is very promising for app owners interested in boosting their conversion rates. For instance, the mobile social gaming company Storm8 saw its revenues from virtual goods grow 1,000% with Amazon’s in-app payment service, which it was beta-testing before today’s official launch.

According to Storm8, this success is a direct result of Amazon’s frictionless user experience – both for consumers, who can reportedly complete a purchase in one click, and for developers, who can integrate it easily.

From Amazon’s perspective, this also represents an additional source of revenue. According to AllThingsD, the company will align with Apple in taking a 30% cut of the transaction.

While this feature is available in Amazon Appstore for Android SDK, today’s announcement also confirms the Kindle Fire’s multimedia ambitions. As a matter of fact, the appeal of Amazon’s first tablet goes well beyond the e-books and magazines its e-readers focus on:

“Kindle Fire already has a well-integrated storefront and marketplace to distribute mobile games. By enabling in-app purchases we are able to be more flexible in pricing. We can release free games, provide updates, and enhancements, and continue to monetize,”  says Social Gaming Network’s senior vice president Licensing & Distribution, Michael Ritter.