The Apple's Appstore has coupons for free installation (up to 50 coupons per release).
I have also designed my own billing system, which has server-backed "free trial", time-limited purchases, and of course "we want to thank you this much" free orders. You can see it in action in my GeeTasksLite iPhone app. I'm thinking about selling this billing system as a library and a service (the server side).
I have also designed my own billing system, which has server-backed "free trial", time-limited purchases, and of course "we want to thank you this much" free orders. You can see it in action in my GeeTasksLite iPhone app. I'm thinking about selling this billing system as a library and a service (the server side).