如何使'android unlocker'应用程序更安全地对抗破解者？

For the paid version of my app I'm opting for the unlocker app route because it's easy to implement, allows for individual stats in the Developer Console but mostly because I wouldn't need to maintain 2 code bases (one for the free version and another for the paid version). Even If I used a CVS (which I do) it would still be a pain in the neck to keep merging features and bug fixes. The unlocker app is much easier to implement overall...For the paid version of my app I'm opting for t