How can I create a software patcher for OS X?

Question

I'm building some software for OS X that isn't distributed through the Mac App Store. My software allows users to download different modules uploaded by various people too.

How can I create a software patcher to patch my software, as well as update modules that users might be uploading when necessary? I've looked a bit into diff and patch, which come with OS X but they seem to be largely for plaintext.

Any ideas? I've been googling but I'm a bit stumped which is surprising since software patching seems to be in most applications.