Amazon is working with a select bunch of developers to pilot in-app purchases for its Kindle Fire tablet. Bloomberg quotes fitness app developer Skimble as saying the trial is “still kind of in its early stages, but we’re very optimistic about it”. The lack of IAP remains a hole in Amazon’s Appstore feature set, given their popularity on both iOS and general Android devices. Mashable notes that analyst IHS has predicted that IAP will rise from $970m last year to $5.6bn in 2015. In separate news, research from CCS Insight and Distimo has been putting numbers to daily revenues from Apple’s App Store and Google’s Android Market. It claims iOS apps generated $5.4m of daily sales in January, versus $679k for Android Market. IAP accounted for 60% of the two stores’ total revenues.