Android market selling upgrades
<p>Im new to android development and I have a question about selling in the google android market. How do you sell upgrades to customers?  For example if I had a free app that I would only allow the app to run for x number of minutes before updating and then have a paid version that would not have the limit. Do I have to have to publish 2 versions of the app or is there a way within the app to allow them to "unlock" the app?  What about premium content like extra features?  Thanks! </p>
