On Mac OS X and Windows H9 Control uses Amazon payments, which isn't available world wide. We looked into using PayPal's payment service, but at the time we were implementing this feature PayPal's service (for in app purchases) was still in beta and had obvious problems. So, that's why we went with Amazon's system instead. If you have an iPhone, yes, please use that instead as Apple's in app purchase system has world wide support.
