The great danger in the fight against piracy is that it's so damn interesting. You can spend months playing cat and mouse with the people trying to crack your schemes, ratcheting up the complexity to insane levels, and every time you come up with a new scheme and get it working you'll feel like a million bucks because you Won(tm).

But the people on the other side feel the same way, there are more of them, and in reality, they're not actually hurting your business as badly as your delusions tell you they are - none of them were ever going to buy your shit anyway.

Add features, improve your design, fix bugs, or tweak your shitty description and screen shots in the app store (which, in my experience, will affect sales for most apps more than the first three factors put together). Literally any time that you devote to copy protection is wasted, unless you're Angry Birds (and even then I'm not sure) you're not reaching anywhere near a high enough percentage of the people that would happily pay for your product to worry about the ones that would rather just take it.