Kindle Fire HD. (Amazon)

Amazon Coins, set to launch in May, will work as an exclusive way for Kindle Fire owners to buy apps and to make in-app purchases.

To celebrate the launch, the online retailer says it plans to give away tens of millions of dollars' worth of its new currency to its existing customers to use within the Amazon app store.

Although specific details, such as whether the currency will be valid beyond the US, are yet to be answered, introducing a virtual currency could be one way of giving parents greater control over how much their children spend online and on what they spend it.

Of the announcement, Paul Ryder, Vice President of Apps and Games for Amazon said that the move was partly in aid of its growing app developer ecosystem and would be a means of making it easier for them to reach Amazon customers. "Amazon Coins gives customers an easy way to spend money on developers' apps on Kindle Fire in the Amazon Appstore-and we're giving customers tens of millions of dollars in Amazon Coins to get started," he said.