Amazon has revealed that its Amazon Underground scheme has helped Fruit Ninja developer Halfbrick to double its Amazon Appstore revenue since the launch of the app, while Rovio has seen its revenue triple.

The two-month-old model allows users to download and play games without paying, with free-to-play games offering up a large number of items that would otherwise be unlocked through IAPs for free.

Developers are then paid $0.002, directly out of Amazon's pocket, for every minute played.

Look after the pennies...

“We’ve been thrilled with the performance of Jetpack Joyride and Fruit Ninja as part of the Amazon Underground program in the month since launch,” said Shainiel Deo, CEO of Halfbrick Studios.

“Thus far we have doubled the downloads and revenue from our apps in the Amazon Appstore and most interestingly, customers are engaging with our in-app purchase content within our games at an extremely high rate."

And indeed, Angry Birds developer Rovio has reported even better results.

“We included four of our popular titles in Amazon Underground at launch, aimed at reaching as many fans as possible in the Amazon ecosystem,” said Tero Raji, SVP of Game Business at Rovio.

“In the first month since launch of these games, the Amazon Underground model has brought us up to three times more revenue compared to the same games’ user revenue in the Amazon Appstore previously.”

Amazon also revealed that the Amazon Underground app has tripled its content in the last two months, adding such games as Monument Valley and Dumb Ways to Die 2.

The app was initially met with mixed views from both our Mobile Mavens and Monetizer Mavens, and we didn't have a particularly favourable view of it either, so it's interesting to see the app working for some of the bigger mobile companies, although obviously in neither companies' case, do we know any absolute revenue figures.