I have a free android app, and I will be adding a bunch of new features that will require unlocking by purchasing a pro package (seperate apk). However, I need to test these new features, and I want to offer my beta testers the pro package for free (as a reward/incentive for testing). Is it as simple as just sending them the pro apk to install over dropbox? Or would this pose a security risk for allowing my pro version to be installed on a device where it wasn't purchased through play store?
How exactly can I go about handing out free access to the pro package?