Do you normally read through people's comment before replying them? I doubt if you do because of you did you won't have replied with this type of post.
Everyone is skeptical if the apk.zip file that you intend to sell isn't going to steal the information of those that have unzipped it in their devices? Because for you to have thought of helping other steal the private keys of an innocent person I'm sure you might be capable of stealing those that are going to patronize you.
Op, why don't you take this idea of yours and channel it into something more useful rather than engaging in an unethical act. You'll be surprised of what you'll be able to build rather than for you to waste your talent on stealing private key/secret phrases.