Design In-App SDK for Android

We want to develop a SDK to connect our Mobile Apps to our billing gateway via HTTP/XML. We would like to create a standard easy to use SDK, which would support Android Apps or .APK Files. This SDK would provide plugins on a standardised way to use in-app payments for a specific mobile framework. The SDK should have support for Native Android Application such as the below: [login to view URL] The SDK should also have support for other platforms to use the mobile framework plugin as per the sample below: [login to view URL] How does the process work? User wants to perform the payment within our 3rd party applications and taps on the PayByMobile button. Your library pops up a dialog box, displaying localized information about the payment. User taps on the Yes button to confirm the payment. Transaction completed and the 3rd party application is triggered via the appropriate callback method. Please do not bid if you do not have experience with these sort of projects.