Well, you can lock down the device so that the end user doesn't own it, doesn't have root, and can't inspect your binary/data outside of your exposed interface. Which is exactly what iPhones and many Android vendors attempt to do.
Indeed you could personalizes the keys for every user. So you could detect a leaked private key that is widely used and proceed against. Still that wouldn't hinder personal further use of that private key, e.g. for exporting data (similar to breaking DRM).
I'm sure there are additional techniques to obfuscate the private key, but relying on locked down devices isn't possible in the Android ecosystem. You don't need a device at all to perform the steps outlined in the article.