How to migrate from a paid android application to an application paid for with in-app billing?
<p>I currently have two versions of my app in the Android market, a paid one and a free one. But I want to integrate in-app billing into my free application, and charge customers on a subscription base, for a lower price than the current price of the paid app. </p>

<p>But how should I handle this for existing customers? It seems unfair to let them pay again for use of the paid functionality, while they were the early adopters of my application. Ideally I implement something that will give the existing users access to the unlocked functionality in my free application. </p>

<p>Any ideas of how to accomplish this? An outline of a good approach to take is enough, I don't mind to do some research on how to actually implement such an approach.</p>
