Ask HN: Best way to market an Android app?

I am working on my first mobile application, which in a nutshell is a camera that asks for a password when you start it and then uses AES to encrypt all photos taken in that session, so that plain data is never written to a storage medium.

I intend on selling this app and releasing the source under a non-commercial license, applicable only to licensees (i.e., once you buy it, you have a non-commercial license to modify and share changes).

What's the best way to market this application? It seems like it will be difficult to break into the Market where there are millions of applications, especially when there are several "vaults" that purport to keep data safe (though they really just move files around so that applications don't see them anymore).

What advice do you have to help a no-name developer successfully market a useful application?