I am developing an android app and I am planning to publish it (paid app). I have heard that it is very easy to pirate Android apps (much easier than iphone). I was wonderin
have a look at the google play licensing framework.
http://developer.android.com/guide/market/licensing/index.html
this is your best choice.
Google Play Licensing is a network-based service that lets an application query a trusted Google Play licensing server to determine whether the application is licensed to the current device user. The licensing service is based on the capability of the Google Play licensing server to determine whether a given user is licensed to use a given application. Google Play considers a user to be licensed if the user is a recorded purchaser of the application.