bensack

Check out PayPal's new adaptive payments (or other similar services). I agree with byoung2 (though I don't have expertise in this area) -- you can receive a preapproval to charge funds once you have the amount needed to purchase through Amazon.

You'll probably need to charge a service fee, since the amount you'll get from your payment processor will be assessed their service fees.

With all the buzz around X.commerce, I'd definitely check them out -- all sorts of promise for easy group payments coming from them in the last few months.

A great lightweight solution to a universal problem -- there's simply no way to fully test an app for all the possible environmental conditions that might cause errors (prior to a release). I like that the SDK is microscopic and doesn't require apps to ship with debug symbols. Debug symbols can increase the size of an app exponentially, so this is a huge space saver. Wayne and Jeff know software, and I wouldn't expect anything less than an elegant utility that does what is needed, and doesn't bloat up the app and cause errors of its own. I expect great things from these guys.